03 · WHO'S OUT
Who's Out
Privacy-first friend availability app, built on iOS 27
The situation
Built at the IndeHub WWDC26 hackathon, where the challenge was to build something around brand-new iOS 27 platform features. The idea: friends lose track of each other's actual availability — everyone's on their phone, nobody knows who's actually free right now.
Thought process
Most "social" apps solve this by adding a feed, which is exactly the wrong instinct — more content isn't the fix for "I don't know who's around." I scoped it down hard: no posting, no feed, no content, just coordination. The app learns a friend's real availability by reasoning over their calendar, location, and Focus sessions, and nudges you when someone nearby is actually free. It also had to justify constant location/calendar access, which meant privacy couldn't be an afterthought bolted on later — it had to be the architecture.
Engineering decisions
The AI reasoning over calendar, location, and Focus data runs on-device — that data never needs to leave the phone to produce a suggestion. Friend-to-friend location updates are end-to-end encrypted, so the server only ever relays ciphertext, never plaintext location. Sign-in is Apple-only, friend pairing is opt-in via invite codes rather than a public graph, and the whole thing ships with a Siri integration built on the new iOS 27 App Intents / Foundation Models stack — you can ask Siri "who's free nearby?" and get a real, on-device-reasoned answer. It's an iOS app + Spring Boot backend monorepo under the hood.
My contribution
Built as part of the hackathon team under real time pressure — the call to scope this down to pure coordination (no feed) rather than a broader social app, and the privacy-first architecture (on-device reasoning, encrypted friend sync) were the product and engineering decisions I'd point to first.