It has dual antennas and catches 1Seg signals. The video will be viewable on the top screen with the controls being on the bottom one.
No word on whether it will support the programming guide info that is built into the 1Seg signals or not. But hey, they are just doing what the PSP already can, which is ok, because the DS has a better implementation of it.
It will drop on November 8th, presumable only in Japan, and it will cost you about $58. So if you live in a country that has 1Seg TV broadcasts, go pick one up.
Rejoice Japan! 1Seg TV Tuner coming to DS Lite [via crunchgear]