I happened to stumble on an advertisement for a cool looking device that would work with a phone via Bluetooth. It was ideally something that would be used for things like movie times, bus waiting times, or something else small and URL based... kinda like a QR code without the annoying camera part.
So I got a pair of RFduinos to play with it. Programming it is quite simple, you just need Arduino 1.5 or later (which you would need for programming a Yun, Due, and possibly a few other Arduinos) and the RFduino libraries (see this). The library comes with an example program accessible under File-Examples-RFduinoBLE-AdvertisementContinuous.
Of course it does nothing unless you have a device setup to receive it. In the Play Store, there is a Physical Web app that can be used to receive the messages (until these become part of Android... and hopefully iOS, too).
Where This Is Going
Rather than beacon a web URL, I imagine with the proper programming (on both the RFduino side and the Android app side), it could be used to pass a variety of messages. In fact, since the app looks up the description information, that could probably be used for simple messages (e.g. "the plant needs water").
This has some pretty cool IoT and alerting uses. Stay tuned!