This app was mentioned in 1 comment, with an average of 14.00 upvotes
Chicago (and suburb) folks who use android and public transportation should get Ride Chicago:
https://play.google.com/store/apps/details?id=com.dattanlabs.ridechicago&hl=en
It allows you to keep tabs on arrival times for CTA trains and buses, Pace buses, and Metra trains. You can favorite stops you use frequently so you don't have to wade through bazillions of stops just to find yours.
It gives you real-time info on how close a bus is. And man, the Clark 22 buses like to snuggle up to each other >:|
The app has shown me a lot of times when two buses for the same route are really close, so I get to purposely "miss" the crowded front one, and get on the empty follower!
I've been using it for maybe 2 years now and the only time it's "failed" me was when I was trying to find the closest buses when I was all the way out in Schaumburg. Something about my cell strength not being great, plus probably the Pace Bus system, meant it wasn't returning "nearest buses" to my geolocation. And this could totally have been because I tend to turn the automated location service off, so maybe I botched something. A few Pace buses lack the tracker, too, so sometimes you'll see the next bus is due in 40 minutes and BAM! Surprise bus.
Other than that, fantastic app.
Edit: Seems available for iPhone/OSX too.