What's the best mobile app to train for a 1/2 marathon?

I'd like to know too

You find a lot info at www. runnersworld.com.
Use an app for distance and pace training.

Runkeeper is the best for me. It maps your run, gives you workouts, lets you create workouts and even gives you voice coaching like: current pace, average pace, distance. It shows calories burnt and you can load that to their website and from there share your runs on Facebook. The best thing: it is free. No need to upgrade.
Sometimes the workout does not automatically upload to the website, I do it manually then. All in all the best and I've had Endomondo and map my run already tested.
Also great: it lets you choose a playlist to play while your running.
You can use it for all sorts of exercise (running, biking, walking etc)
Hope that helps

what does bump mean?

I heard the Hal Higdon guides are amazing. I have a friend who has trained and run multiple 1/2's and fulls based on his trainings.