This app was mentioned in 3 comments, with an average of 1.67 upvotes
You don't really need them if you use an app like this one, uses your gps to show you the nearest stops on a map
The trimet tracker app works well for getting bus/max route and stop time info quickly. Google maps will still be your main tool for getting around of course
https://play.google.com/store/apps/details?id=com.beagleapps.android.trimettrackerfree
On android i use a simple app called trimet tracker free
https://play.google.com/store/apps/details?id=com.beagleapps.android.trimettrackerfree