I'm reading WIFI Power Amplifier 150Wx2. The nob appears to control power and volume.Details? Pic hard to read. Someone else was selling similar on Mud.
Not sure it @thecrazygreek is still making/selling these. However here is a bluetooth option for FJ40s.
For Sale - Bluetooth Stereo 100% Hidden, only takes up the space of a dash knob! (Custom knob included)I have cobbled together a totally new stereo solution for your 40 series. (or any other car/truck) It only takes up the space of an in dash switch! This is a Bluetooth only, dash mounted, 100watt, little powerhouse! Hooking it up is easy. Supply 12v (it can take 5-24v) switched power. I...forum.ih8mud.com