I have the CD-SR110, but with a different Head Unit (AVIC-F50BT) so maybe this info is not useful for you:
I had the SR110 connected to the car steering wheels with my previous pioneer HU. When I changed to the F50BT, I wanted to keep that. The only way I found was through an IR reciver (Pioneer CA-R-IR.002), as the SR110 works wireless by Infra-red, and the HU remote control input is for cable.
I can control volume, track, source switch and phone control (show the HU phone menu and in a call, accept/reject/hang up). When in AppRadio Mode, track buttons work as the HU track buttons, that is, as "Back" and "option" android buttons. I think these behaviours depend more on the HU that in the remote control.
I've read in this forum that in USA exist companies dedicated to steering wheels interfaces. So maybe there are better options than mine.