I recently did a lot of research in order to gather all the parts needed for the head unit upgrade in my 2016 Scion IM, so I thought I'd share the wealth. I was so tired of the stock head unit's limited functionality, poor Bluetooth connection, and outdated entune app that I decided to upgrade to a double din head unit with Apple car play (also works with android auto jik I decide to switch phones in the future). The parts needed in order to integrate the new head unit into all the factory systems without hacking up the harness is quite extensive but it's doable. The only OEM feature I wasn't able to retain was the microphone but the new radio came with a replacement that was super easy to install. All in all, I spent about $427 to do the upgrade and it was well worth it. My parts list and pricing is as follow:
Dual - head unit - $273.42
Metra 95-8202 - Dash Kit - $10
Metra ISOPK - Screw Pack - $4
PAC RP4.2-TY11 - steering wheel controls Interface - $85
idataLink Maestro ACC-USB-TO2 - OEM USB port Retention harness - $25
Metra 40-LX11 - Antenna Adapter - $7
PAC CAM-TY12 - Backup Camera Cable - $20
Male RCA to Dual Female RCA Y Cable - $3
Hope this helps!