Win CE, mobile or whatever - will do well with WMV - Palm - is dependant on the software that they have - though I think that it may not naturally be able to view any video natively, However - the most universally used codec by both is probably MPEG2.
Software for both are capable of playing those - not sure that you can really stream that though - I think they make flash for both OS's as well - but not sure how well they work.