Buried deep in the list of new features revealed for the L release of Android, whenever that comes out and whatever it will be called when it is, was BLE Peripheral Mode. This addition to Android is part of the Bluetooth Low Energy profile. Previous versions of Android could use BLE-enabled devices, but only as a primary device. The newly-enabled Peripheral Mode should allow apps on any Android phone, tablet, or what have you to send data to other devices.
Android devices can now function in Bluetooth Low Energy (BLE) peripheral mode. Apps can use this capability to broadcast their presence to nearby devices — for example, you can now build apps that let a device to function as a pedometer or health monitor and transmit data to another BLE device.
Example: let's say that, for whatever reason, you keep your health information on your tablet rather than your phone. In 4.4 and lower, if you wanted to keep up to date with your steps on a pedometer, you would have to carry your tablet with you everywhere. (Or, I dunno, just buy a $10 pedometer.) With Peripheral Mode, you can use an app on your phone as an external pedometer and sync it back into the app on your tablet. Peripheral Mode also allows for basic positional detection, most notably used in Apple's iBeacon standard, which commercial developers are eager to use for advertising.
It may seem like an odd distinction, but there are apparently hundreds of developers who have been asking for the feature, not to mention decrying the fact that until now (or indeed, until L is released) it was only available in iOS. Check out this list of developers complaining on the AOSP issue tracker, stretching from September of last year to just a few hours ago.