An anonymous reader quotes a report from Ars Technica: T-Mobile has announced the launch of its "Digits" program, coming May 31. Digits is a revamp of how T-Mobile phone numbers work, virtualizing customer numbers so they can work across multiple devices. It sounds a lot like Google Voice -- rather than having a phone number tied to a single SIM card or a device, numbers are now account-based, and you can "log in" to your phone number on several devices. T-Mobile says the new phone number system will work "across virtually all connected devices," allowing multiple phones, tablets, and PCs to get texts and calls. This means T-Mobile needs apps across all those platforms, with the press release citing "native seamless integration" in Samsung Android phones, Android and iOS apps, and a browser interface for PCs. The new phone number system is free to all T-Mobile customers. Customers can also buy an extra phone number for $10 or by signing up to the $5-per-month "T-Mobile One Plus" package, which is a bundle of extra features like a mobile hotspot and in-flight Wi-Fi.