DutchTab

DutchTab lets you easily split bills between friends or coworkers. It automatically calculates who owes whom based on the ratio of each person's order and their contribution when the bill was paid. You can even send everybody a summary by email from your device. Whether sharing a lunch order with coworkers, dining out with friends or splitting bills with roommates, those who have cash can take care of bills and get their fair part later.

Requirements:

Windows Mobile 5.x/6.x, Microsoft .NET Compact Framework 2.0

Limitations:

3 partakers per bill/2-bill saving trial