Go! Messenger PSP, Headset via PSP Remote. I managed to get a bargain and pick up a Headset as part of a package with SOCOM on the PSP but until I was able to get someone else with a Headset I wasn't able to test it.
Go! Messenger came free with an update of the PSP's firmware,. It's an application that sits on the XMB and can be used for chatting with fellow PSP owners (via Headset, Cybershot camera, or Talkman Mic & headphone) or even to a PC that has the software installed.
The Headset is quite nice the earphone clip over your ears and have a sponge pad on them and a plastic bendy mic from the left ear. Sadly you need the Remote for this mic to work but the headphones can be used for gaming and sound far better than the PSP speakers.
The software it's self is a basic messaging tool but does allow for Voice chat & video chat. It also allows for text chat but could do with a precitive text system like the PS3 has to save time. You can also record and send voice and video messages.
The sound quality is comparable to mobile phones but does have a 0.5 second lag but that's not such a big issue.
I'm aim to have a fuller test soon with the video fuctions. But from what I've found this could work as an alternative to having in game XMB for the PS3 or be used as a repleacement for the poor quality chat of certain PS3 games.
As something that came for free I can't complain.