Radio Upgrade

I would look at aftermarket double din touchscreen systems that run Android so you can use Google Maps and other software. The navigation built into gen 2's is rather outdated IMHO. The advantage of Android is you can use your favorite maps software, and install upgrades as they come out. I personally don't bother as I just have a nice mount for my phone and use an aux in for audio to my aftermarket headunit.

Also, there are kits that would allow you to wire to the existing steering wheel controls.

You're correct that none of the controls on the Prius touchscreen will work with an aftermarket unit (only steering wheel controls if you wire them in using a kit and compatible headunit).

 

I was consdiering this for my 2005 Prius. I would loose Nav, which is not an issues for me because I never use it. This system is Android Auto and Apple CarPlay compatible so it works like Kevin_Denver was mentioning. This system is bundled with a back-up camera but you can buy the system without a camera for $100 less. This system also gives you 2 USB ports.

This is double-DIN. It's compatible with steering wheel audio controls but requires an adaptor to do so. It also requires a wiring harness. Crutchfield is a fabulous company to deal with and they provide lifetime customer support on any product that you buy. –I don't work for them but have bought several home theatre products from them.

https://www.crutchfield.com/p_7004200NEX/Pioneer-AVH-4200NEX-Bundle.html?tp=5684

 

I recommend an Android auto HU either the pioneer nex series or carjoy brand. Look on XDA developers for standalone Android headunits because they sell some with specific faceplates for the Prius. I would get one but I like having nav in my head's up display.

 

I did some research on it just a few days ago. While those Chinese generic Android HU are cheap and rich in futures, the consensus is they fail quickly. Im thinking they use low grade components and we all know how hot cars get in the sun.