Complex trip planning for professionals, but in a different way from Ambulate - not hiking trips, but transactions across Web sites: I really hate the way how today you cannot "properly" book a flight, hotel, train like you would do it in a SQL transaction
BEGIN TRANSACTION
book train
book flight
book hotel
COMMIT;
Only if all three are available and execute the reservation without error do I also want to execute the other ones; that's a prime use case for DB-like transactions, but across Websites. Because no point getting only the flight if I have no-where to stay etc.