This is truly wonderful — from the MySociety man. Currently in private beta, but mainstreaming soon (I hope).
MySociety has done some amazing stuff in the past. This shows that they’re not flagging.
Also: Should have mentioned that this work is supported by 4IP, which is headed by Tom Loosemore and has funding some interesting work. 4IP has an iPhone App deveopment fund aimed at stimulating the development of socially-useful Apps.