I used Scheduling and Invoicing as well. I decided to spend the time to build a custom app myself. It's not too difficult, the work orders are just Activities (filter them by type - work order).
This actually worked to my benefit, as there were many things in the old work order screens that I didn't use. My new screens are (or will be.. they're almost done) much more clean and streamlined as a built them to my exact needs.
Are you using a pre-existing android app, or are you building a custom one?