This is kind of neat.
Gorischek Design’s Tipping app allows you to quickly calculate how much to tip on your iPhone, iPod touch or iPad without having to unlock the device.
The app allows you to calculate 15%, 20% and 25% on a tip, enter the amount and get back to your meal.
Tipping requires iOS 8.0 or later to install and run and retails for $1 in the App Store.
Via the App Store