Also, the PS3 becomes unusable in any other form while its in Remote Play mode. And...
In remote play, the PS3 becomes an access point, and the PSP needs to hook up to it Ad Hoc. At least that's how it went for us. Mainly, because the PS3 wouldn't let us set up an AP that was WEP, it wanted to go to WAP on our G network. Anyhow, its fine: the PS3 remained connected to our main internet access point while this was going on.
Also, the PSP isn't doing any sort of PS3 interface in emulation. It's actually streaming a video of the PS3 interface over WiFi. Like the LocationFree TV. In fact, its probably using the same code, since the PSP has the LocationFree client built in.
All Things PS3 [Gizmodo]