Stripe iOS SDK - Accept both Apple Pay and credit card payments easily on iOS
WiFi Map - A crowdsourced list of routers and passwords
Pilgrim SDK by Foursquare - Location data to understand & engage with your customers
Get Free Fucking WiFi - Find the best fucking WiFi just around the corner.
MightySignal Top SDKs - Most used SDKs in top 200 free iOS apps. Learn what to use.
Instabridge - Crowdsourced free wifi (now on Android)