I did not know that there is more than one Sony PSP TV connector on the market. We reported about the PSP on TV in October. Lik-Sang has published a review about the PSP2TV adapter kit.

The PSP2TV Sony PSP TV adaptor kit actually requires to open up the Sony PSP and by doing this void your warranty. The PSP On TV is works without voiding the warrenty of the PSP.
Lik-Sang is also offering a warranty safe version, but it will not be released until December.
The cool thing about this PSP TV adapter is that it also lets you connect a Sony PS2 controller. Lik-Sang warns though that the required modification is a bit tricky. The image quality on the TV is comparable with the PS One. Additionally it works better on 16:9 TVs.
Read the full review. The NTSC version of the PSP2TV adapter is in stock. The PAL version comes next week.

I think the 4GB HDD for the Sony PSP is a more useful accessory.