Tripwise

Split any bill fairly and convert currency — fully offline with cached rates, made for travel.

Splitting a bill fairly is harder than dividing by the number of people whenever the shares are uneven, and the version that causes friction is settling up afterwards — a group of five owing each other in both directions needs netting, not a list of transactions.

Currency is the travel-specific complication. Cached rates matter because connectivity abroad is unreliable and roaming is exactly when you least want to depend on it. Worth knowing that the rate your card actually charges will differ from the mid-market rate, so a conversion is an estimate for splitting rather than an accounting record.