Rest in peace, Pokemon GOunofficial companion map apps. And long live those same apps.
The run enjoyed by apps like GO Gear and services like Pokevision.com was a fun one. They worked by using Niantic's API for Pokemon GO, essentially peeking behind the curtain to determine exactly where different Pokemon would spawn and how long they'd stick around.
While some players decried them as cheats, there's no doubt that having the info they provided made the game a lot more purposeful than simply stumbling around and hoping to find pocket monsters you'd never encountered before. But as the saying goes, all good things come to an end, and with the game's most recent round of updates, Niantic more or less neutered those apps, explaining that the extra strain they added to the game's servers was hindering the experience of the masses.
Thus, Pokevision has gone from essential to useless just like that, and apps that worked in similar fashion have also been cut off at the source. What hope is there now for Pokemon location apps?