Video: Keeping track of which Pokemon are spawning in your area in Pokemon GO usually requires you to keep your phone open and running. Over on Adafruit, they show off a way to build your own Pokemon detector using a Raspberry Pi Zero. This guide walks you through the set up process to build a little device that will alert you with a light anytime a Pokemon is near. The catch here is the fact this is against the terms of service with Pokemon GO, so you're making this at the risk of getting banned at some point. Still, it's a fun project to make for yourself, even if you don't end up using it on your main account. Head over to Adafruit for the full guide.
Raspberry Pi Pokémon Finder [Adafruit]