Great...
It might not seem really good for people not interested in tabletop games, but tool that easily allows you to roll 20 d20 dice at a time, and also works as spare set of dice is very useful, especially if DM has tendency for epic battle scenes (like, 30 people on both sides, players amongst them) . Great.
As for ideas - how about adding other dice than d20 for group (called initiative, but has more uses with some imagination...) rolls? It would make it way more versatile tool, good not only for D&D... But it is great, still.