Pinpoint
Location sharing without the surveillance business.
The apps that let a family see where each other are come with a cost that is not on the price tag. Most of them are advertising businesses, and the product being sold is a live map of where you and the people closest to you spend your time.
Pinpoint does the same job without that arrangement. Invite-only groups, live location among people who chose each other, alerts for arriving and leaving, and an emergency button. Nothing sold, nothing shared outward.
Invite only, and honest about it
A group is closed. Sharing is a choice each person makes and can switch off, and the app says plainly on screen who can currently see what.
Place alerts that don't cry wolf
Alerts for arriving somewhere and leaving it, tuned hard against the false alarms that make people mute this kind of app. That tuning was most of the work.
A battery that survives the day
Location accuracy adapts to what you are actually doing, driving, walking, or sitting still, rather than holding the GPS radio on from morning to night.
An emergency button
One press sends your location and a message to everyone in the group.
This started because the commercial app we were using kept getting worse, and it was never really ours to begin with.
Building it taught me more about mobile platforms than anything else I have made. Keeping a location app alive in the background on a modern phone, which is actively trying to shut it down to save battery, is a genuine engineering problem.
What it proves: Cross-platform mobile, live data, and the unglamorous discipline of making software keep running when the operating system would rather it stopped.