If you're interested in the Windows Mobile Platform, the Cingular 8125 and T-Mobile MDA (same phone, different body) along with the Spring PPC 6700 run the Slingbox software for viewing. I do not know how well the video looks as both use a slower data network than the newer Verizon and Spint EV-DO networks.
As for Mac synicing, you'll have to get extra software to do that, like Missing Sync for Windows Mobile.
Personally, I had the 8125 for a week but then returned it and went back to my Treo 650 because the 8125 was incredibly hard to use one-handed without the syllus. That and you'd have to manually quit programs by going into the memory manager otherwise the device would get too bugged up and slow.