Remote control robots are nothing new. Using Bluetooth isn’t all that unusual, either. What [SayantanM4] did was make a Bluetooth robot that accepts voice commands via his phone. The robot itself isn’t very remarkable. An Arduino and an HC05 module make up most of the electronics. A standard motor driver runs the two wheels.
The Arduino doesn’t usually do much voice processing, and the trick is–of course–in the phone application. BT Voice Control for Arduino is a free download that simply sends strings to a host computer via Bluetooth. If you say “Hello” into your phone, the robot receives
*Hello# and that string could be processed by any computer that can receive Bluetooth data.
Naturally, this wouldn’t have to be a robot, although the program description repeatedly mentions robots. You could just as easily use it to add voice commands to a homebrew home automation system, for example. And despite the app’s name, whether or not you actually have an Arduino on the other end is up to you.
If you wanted to do voice control without sending data to some evil overlord and depending on a cell phone, you could check out the MOVI board. Sure, that project is a clock, but we’ve seen voice controlled robots before, too.