Ask HN: How do you split app revenues?

When developing an app with friends/partenrs, how do you handle splitting revenue and expenses? Do you use an Excel spreadsheet, pay a 3rd party, or use an online tool? I would love to know what the market is doing.

We have built a pretty robust site for ourselves and I think it may be generally useful to all small dev shops to track expenses, payments and revenue.

Thanks for any and all input!