I'm working on an automated escrow with 1% fee that has no minimum. I've done live tests with amounts as low as 2x the transaction fee, next one I'm running is going to be same as transaction fee (I'm sure you could go lower...but why?).

PM me if you want to help test it, it's fully functional on the public facing side, but I haven't made it public since I still need to write an admin panel.

edit: I've successfully tested .0005 in escrow. 0.0005 is escrow, 0.000005 is the 1% fee.