There are lots of dice rolling apps on the store - but they're mostly about rolling individual dice, or rolling a handful of dice and adding the results.

I play Warhammer - so I wanted an app which would roll bucketloads of dice for me, allow me to reroll dice when the rules permit, then allow me to select dice which meet a threshold and roll them again.

It's quick and simple, and when you're not in the mood for throwing large handfuls of dice, it can do that for you.