Could be perfect but

Splitting a restaurant bill by entering each persons COEFFICIENT? Thats not user-friendly at all!
Heres an idea: split the bill equally at first, then let us edit amounts. For each of them, add an On/Off button for "automatic adjustment", so each time we edit one amount, you can automatically adjust the other ones equally. Maybe always keep one amount for auto adjustment too. That way, the total will never be wrong.

TouchezEtoile about Share-a-bill