I built a Mac app to stop exceeding my mobile data cap

#showdev #swift #productivity #development

Ever tethered from your iPhone for "just a quick Zoom call" and ended up burning through half your monthly data?

Yeah, me too. Multiple times.

The problem

macOS doesn't distinguish between your home WiFi and your iPhone hotspot. Activity Monitor shows total bandwidth, but not "how much data did I use specifically on this limited connection?"

Existing solutions either:

TripMode ($15/year) - Overkill. I don't need app blocking, just awareness
Bandwidth+ (Free) - Doesn't know the difference between hotspot and home WiFi

So I built HotspotPeek

A simple menu bar app that:

Detects hotspot connections using NWPathMonitor.isExpensive
Tracks data per session and per month
Supports multiple profiles (personal phone, work phone, travel MiFi)
Alerts before you hit your cap

Technical bits

Built with SwiftUI + AppKit (NSMenu for native feel). Uses:

NWPathMonitor for connection type detection
CoreWLAN for SSID identification (to auto-switch profiles)
Pure system frameworks, no external dependencies

macOS 14+ only because I wanted to use the @Observable macro.

Lessons learned

Sweet spot matters - Found the gap between "too basic" and "overkill"
Location permission UX - Needed for SSID access on Sonoma+, had to explain clearly why
Menu bar apps - NSMenu > NSPopover for authentic macOS feel

This is part of my "Peek" series - simple utilities that surface hidden macOS info: