Go ahead, I dare you to explain to me the utility you derive from playing 1080p video on your iPhone 3GS. A post on a Chinese forum suggests that the phone is perfectly capable of playing 720p and 1080p when encoded with H.264; Apple currently limits playback resolution to 640×480. The angle right now is, “How dare Apple artificially limit the resolution that we can play?” Well, one, it’s Apple, what do you expect and, two, can image how quickly the battery will deplete when playing 1080p video?
A forum-goer was able to get around Apple’s restriction, playing a 1080p video at 30Mbs. (Really? My stupid MacBook would scream in horror trying to play a 30Mbps video, even when using Plex.) So, technically, yes, it does appear to be possible to play “Full HD” video on your iPhone 3GS.
Of course, watching such video on your iPhone is probably overkill, but I guess Apple could, one day, release an adapter that would allow you to output 1080p video from your phone and onto an HDTV. You’d probably need to keep your iPhone plugged in for the duration of that playback, so it’s not exactly going to be elegant.
But, if it can be done, mazel tov in your general direction.