My friends and I are heavy users of BillMonk so your service definitely interests me.

However for the example in your video, BillMonk is clearly superior. With BillMonk, one person pays, takes home the itemized receipt and enters it in. Then for each item, they specify who ate or shared it. BillMonk totals everyone's part and automatically assigns the debt. The tax and tip are also split based on each person's total percentage of the bill.

It seems with Piggy Back, the payer would need to figure out each person's split manually and file multiple debt reports. How are you improving on BillMonk's model?