In Roodrive, I use 137 for straight driving (swiping up or down) and for straight turning (swiping left or right) and 145 if the user wants to drive and turn at the same time. See the documentation for details or look at Roodrive.java in my source code. Then you drive the Roomba with the high-level 137 command, where you specify speed and turning radius, or the somewhat lower level 145 command, where you specify individual wheel velocities. To accept movement commands send 131, which puts the Roomba in safe mode (so it won't drive off stairs, or drive away while plugged in, etc.) To connect, send a 128 byte to the Bluetooth device that is connected to the Roomba. If you want to write your own software for controlling the Roomba 500+, the crucial documentation is here. So instead I wrote Roodrive (source code here), a simple Roomba Bluetooth remote app that is controlled by swiping in a semi-transparent square on the screen that shows up on top of an app displaying video. I tried using an xposed module that let me run two windows on the tablet, one with a Roomba remote control app and the other showing the video, but that was a clunky way to do it. The only problem was how to control the Roomba from the device that was displaying the video. You can do this with Skype or Google Hangouts, or with a webcam app. The idea is that one Android device stands on the Roomba and streams video which is displayed by the other.

A stand for putting an Android device on a Roomba (this can be just a couple of pieces of wood and some rubber bands Velcro on the stand and the Roomba makes things more convenient).

Bluetooth Roomba adapter (I used a Brainlink set up according to this Instructable).

Two Android devices (e.g., a phone and a tablet).

Roomba 500+ (if you have an older Roomba, you'll have to tweak the code).

Here's what you need on the hardware side: This particular project for me was almost all software development because I already had all the hardware.

It's even more fun to have a first-person view while doing so. It's fun to drive a Roomba around by remote control.

Roomba game