Starbucks will soon let you tip a barista straight from an iPhone. An update to the iOS Starbucks app, due March 19th, will allow customers in the US, UK, and Canada to tip digitally with their phones while paying for a coffee. You’re typically free to tip any amount in cash at a counter tip jar, but Starbucks is limiting digital tips to just 50 cents, $1, or $2 through the updated app. Starbucks move to digital tips compliments the impressive growth of its mobile apps.