I wrote a program on Android that interfaces with Arduino using Bluetooth and displays battery percentile, Missed calls and unread SMS messages on a 7 Segment display.
For me it is useful and has value, but I admit it was also a good way to learn Android programming. All code is in herehttp://www.instructables.com/id/Missed-calls-and-SMS-Notifier-Accessory/.
Wow, really a great Thing!
I´d love to use it through W-Lan, also.