The Solisto is not there because you're the first person to report on it. It would be lovely if you could add it to the chart so other people could see it doesn't work currently before they go out and buy one.
The wiki page attempts to explain what needs to be done to support these things, but perhaps not clearly enough. In short :
1) Someone needs to finish support for the serial port presented by the "dock" port on the bottom of the ipods. This has been started, but isn't ready for inclusion in the main line of Rockbox yet.
2) Someone then needs to write support for the Apple Accessory Protocol (AAP)as far as it is understood. The good folks at the ipodlinux project have documented it a good deal, but it's not 100% yet.
3) Someone needs to interface the AAP to the Rockbox code so that all the remote control features work properly.
This is NOT a trivial piece of work.