I can do this, according to my understanding, you have your server side ready, and REST API is ready to use. right ?
I am the professional developer in Android platform, and have more than 6 years experience on this platform. I did many projects such as Barcode Scanner,certificate management, GPS tracker, Customized Lock Screen, Social App(integrated email/facebook/twitter) and fancy ToolBar etc.
And the delivery time and price are negotiable.
Thanks!
Alpha