The ClieSource Forums are an excellent source of info. It turns out that installing the movierecorder.prc (version 1.3) from a UX50 onto the TH55 allows it to record movies. The problem is getting that file….
Isn’t Google great? If that doesn’t work out for you, try searching at the Palm User Message Board, where you might just find it.
Here’s the trick: you can’t just install the app via Palm Sync. You’ll have to copy or sync it onto the Memory Stick, then copy it to the internal storage. Happy video!
[UPDATE]: I found more info and a better source for the movie recorder here.
For example movies shot using the Clie TH55, follow the links in this story about Cliff’s Piranha.