strain gage connected to smartphone

Hey guys, I'm planning to make a kind of smart scale connected to my smartphone (I would like to have the weight displayed directly on my phone), by using a strain gage, an Arduino board (I still don't know which one, probably the Mega 2560 R3, or its cheaper, compatible version) and depending on the connection type- a HC-05 Wireless Bluetooth RF Transceiver, or a Xbee chip.
I would like to hear your advice regarding the type of connection that I should use, and how to wire it all up together.
Thanks a lot :slight_smile: