There is exactly no synergy effect between desktop and handheld devices. There isn't even the same kind of market between them. Look at the appliances on the desktop, then look at the "same" kind of tools on handhelds. Can you imagine using the same user interface on both? Or wouldn't you rather think that the appliance that uses the UI of one on the other is "doing it wrong"?
For reference, see Windows 8. Or WinCE for the reverse. It just doesn't work right, look right or feel right.
There is also not the same market in any other area, be it games, development (just in case anyone is crazy enough to actually develop software on a cellphone...) or ANY other area. It just doesn't work that way.