Don't know if Android numbers are helpful to you too (maybe just the contrast will be interesting), but here's my experience in the Android market: a) 1 b) paid c) I posted in a dozen message board threads or so where people were looking for such an app, and I've diligently answered every e-mail I get about it. d) It's been in the Market for about a month and a half, and I've made a little over $2000. Hard to give a per-month answer as I don't know if it will taper off and run out of customers. ;)