The Hacking Package was what I was referring to. I used the same package on my dear departed Pocket PostPet, and I ran into the same limitations. I had to live without system tray icons, but SQ did make a nice replacement for the desktop:
http://hp.vector.co.jp/authors/VA003011/
There may be a way to create a Control Panel, but I haven't figured that out yet.
When it says "full CE 2.12," that's a bit misleading. CE 2.12 wasn't a platform release - it was used strictly for embedded systems like in these devices, so it lacks many of the APIs/DLLs of H/PC Pro. Unfortunately, these devices also have pretty small RAM, so there's also little room for runtime libraries like eVB.