With this interface you can program a network equipment from your mobile phone.

You can find the module ready from eBay. I change the RS232 to a male one as the build in female is opposite from what is needed. I used a common spare battery from a mobile phone. The module has build in charger for the lithium battery. You connect a mini USB adapter to charge. It has two leds one for power and one for displaying charging status. It has two modes selected with the switch, you can read the manual for info about them. I used fishing fiber to to display the light from leds outside.Use a plastic case not a metal one as it permits the 2.4 GHz and not shield them. Do not forget to use a small fuse in series with the battery.