GPS checker is a useful tool for anyone who uses GPS on their iPhone, be it with sports (Runtastic/Nike+) or games (Pokémon GO).
This app can lock the GPS signal before launching any other app, which results in major speedups when using apps that struggle in this process.
Morover, GPS checker allows you to see the raw data from your iPhone GPS chip, so you can be sure that everything is working fine before hitting the road or going on your sport sessions.
Warning: GPS checker rely on GPS for accuracy. Continued use of GPS running in the background can dramatically decrease battery life.