I just shipped a small Android app called MeasureKit — nine phone-sensor tools in one place (compass, ruler, sound meter, magnifier, bubble level, clinometer, vibration meter, protractor, light meter). Before deciding what to put on its first Play Store screenshot, I wanted to know what people actually hate about the apps that already own this category. So I pulled every public review I could get for the most-installed app in each tool's niche and read the low-rated ones.
This post is about the category, not my app. If you build anything that turns a phone sensor into a "measurement", the pattern below will look familiar.
What I looked at
| Tool | App | Installs | Rating | Text reviews | 1–3★ |
|---|---|---|---|---|---|
| Compass | Digital Compass | 10M+ | 4.66 (616k) | 6,000 | 765 |
| Ruler | Ruler (nixgame) | 10M+ | 4.37 (115k) | 4,411 | 556 |
| Sound meter | Sound meter: SPL & dB | 5M+ | 4.62 (53k) | 3,271 | 294 |
| Magnifier | Magnifier + Flashlight | 10M+ | 4.86 (242k) | 6,000 | 187 |
| Bubble level | Bubble Level (gamma) | 10M+ | 4.69 (334k) | 6,000 | 435 |
| Vibration | Vibration Meter (sira) | 5M+ | 4.39 (36k) | 3,118 | 368 |
| Light meter | Light Meter - Lux Meter | 1M+ | 4.78 (17k) | 1,316 | 86 |
Two more (a protractor and a clinometer) had one review each, so they're out. Method, so you can reproduce it: google-play-scraper (Python), languages en + ko, newest first, up to 3,000 per language per app. Play only returns reviews that have text, so those are text reviews, not total ratings. I then bucketed the 2,693 reviews rated 1–3★ by keyword and sorted the buckets two ways: by count, and by how many other people clicked "helpful" on them.
The complaints, ranked
| # | Complaint | Reviews | 👍 helpful votes |
|---|---|---|---|
| 1 | Too many ads | 482 | 1,147 |
| 2 | Not accurate | 223 | 567 |
| 3 | Scale / units wrong | 136 | 868 |
| 4 | Confusing / can't get out | 76 | 198 |
| 5 | Calibration / sensor | 58 | 345 |
| 6 | Privacy / tracking | 37 | 337 |
| 7 | Paywall | 31 | 180 |
(The keyword classifier is crude — a "crash" bucket got 453 votes from a single Korean compass review that is really about accuracy. I only quote reviews I read myself.)
Accuracy is not the #1 complaint for a category whose entire job is being accurate. Ads are, by count and by votes. And the ad complaints aren't "there are ads" — they're about a specific trick.
1. Ads that cover the Android navigation buttons
The most-upvoted English review in the whole set (136 👍), on the sound meter:
"Once opened, you can't exit the app. Once opened, all the usual Android buttons and menus disappeared."
And the next three, same app (81, 72, 71 👍):
"It purposely obscures access to the android soft buttons, uses intrusive ad tactics to increase your 'interaction'…"
"The ads run right on top of the buttons for the back button and the home screen."
"…positioning the ads into the screen space that the bottom bar, where all the close app controls are, along with a very short reclose time is kind of devious"
On the bubble level (42 👍): "the ads pop up every time my screen turns off. There is no close button so I have to hit back." A level is something you hold with one hand against a shelf. Turning the screen off is the use case.
2. The ruler that needs a ruler
The single most-upvoted review in the dataset is Korean, on the ruler (192 👍):
"It looks really convenient with all the fitting functions, but the divisions don't set themselves per phone, so if you want to use it you need an actual ruler anyway. I wonder if the people leaving reviews had 1 cm set correctly, lol."
That's the whole problem with a screen ruler in one sentence: Android reports a nominal DPI, real panels differ, and if the app doesn't make calibration obvious, every measurement is off by a few percent and the user finds out at the worst time. Another one (71 👍) tried to calibrate against a real 4-inch mark and found the 1, 2, 3 inch marks still slightly misaligned — the calibration UI itself was imprecise.
Tablet users notice it most (15 👍): "on a tablet the size is way off."
3. The sound meter floor
61 👍:
"It doesn't matter how quiet it doesn't display below around 30–35 dB. Makes me wonder if it's a calibration issue or a compatibility issue with my phone or if my phone's mic is just bad."
This is a real physical limit — phone mics and their AGC don't go much lower — but the app gave no hint, so the user blamed themselves and the app equally.
4. Privacy consent as a wall
124 👍 on the ruler, 51 and 39 on the compass:
"It takes over half an hour to manually go through and uncheck every data tracking company that wants to track your data through this app."
"Privacy nightmare! It's a decent compass but I don't appreciate several hundred companies claiming they have a 'legitimate interest' in tracking me… you have to disable each individually."
A compass. It needs one sensor and zero network. The users know that, which is why the reaction is so strong.
5. Units and background
Vibration meter (64 👍): "Uses Mercalli instead of any unit of measure of amplitude or frequency. Completely useless." And (50 👍): "does not work in background, once cellphone is in standby state screen goes dark, the app does not detect anymore."
What I took from this
- In a tool app, the ad placement matters more than the ad count. Nobody in 2,693 low reviews complained about a banner in its own slot. They complained about ads over the back button, ads on screen-off, and ads with a 1-second close delay.
- Say what the sensor can't do, on the screen. The ruler and sound meter reviews are people discovering a hardware limit with no warning. A one-line "phone mics aren't calibrated instruments — adjust the offset in settings" would have turned a 3★ into a shrug.
- Calibration has to be a first-class feature, not a hidden menu. The ruler's top complaint in two languages is the same thing.
What MeasureKit does about it (and what it doesn't)
Only things you can verify in the app or the listing:
-
No interstitial, app-open or rewarded ads.
InterstitialAd,AppOpenAd,RewardedAd: zero occurrences in the codebase. There is one banner in a reserved slot at the bottom of the screen — it never overlays the tool or the system buttons — plus a dismissible native card at start and on exit. - No subscription, no billing code, no login, no server of ours. The only network traffic is the ad SDK.
- Permissions are per tool and optional: mic (sound), camera (magnifier), location (compass — true north, sunrise/sunset, altitude; the compass works without it). Deny one and only that tool shows an in-screen note.
- Ruler calibration is in Settings and on the ruler screen itself (a CAL button), with cm and fractional-inch scales.
- Sound meter shows dB(A) with a user offset, and the screen says outright that a phone mic is not a calibrated instrument.
- Vibration meter reports m/s² and g (RMS, peak, 8-hour limit), not just a Mercalli word.
- Compass shows a sensor-accuracy warning and only applies true-north correction when it actually has a location.
What it doesn't do: it won't measure vibration with the screen off (no foreground service), it's a screen ruler, not a 3-metre tape, and its sensor readings are only as good as your phone's — same as everyone else's. It shipped this week, so I have no stability data worth quoting. If it breaks for you, tell me; that's the data I don't have.
Play Store: https://play.google.com/store/apps/details?id=com.eltacrew.measurekit
Data collected 2026-09-12 with google-play-scraper. Quotes are verbatim from public Google Play reviews; the Korean ones are my translation. I'm the developer of MeasureKit; competitor names are used only to identify the public listings analysed.
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