A free app for Android, by Rez Mobile.

TreKing is the only all-in-one app you’ll need to get around Chicago with transit. It’s the most popular and award-winning public transit app for Android. You can get detailed information on every CTA, Metra, Pace, and South Shore Line train, bus, and street car.

It’s easy to get started. You just need to download the app, enter your station ID, and you’ll see all the available vehicles at your station. You can also see how many vehicles are available at each station and how long it will take to get from your location to the next station.