I second Runmeter - I love it so much I posted about it the other day. The customisation options are fantastic, so you can have a main page showing the info you choose, and colour things the way you like. So I have time, distance and calories in white, steps in green, and heart rate in red. The time stops if you stop and a smaller timer keeps track of your stopped time independently of the walking / running time.
You can have a screens showing your pace info, so time / % of your walk / run in customisable pace intervals, and the same with heart rate zones. And also screens showing current / average and max heart rate and current / average and fastest pace.