sony is selling the HDCX-300 HD camera head with HD-SDI output.
does anybody knows about this ?
Could be an alternative to build an HD-Camera with separate recorder ?

I've seen these box cameras a long time ago. Ikegami actually has one that you can buy to make it almost an ENG setup. (Shoulder mount and handle and viewfinder attachmetns).

These could most definetly be used as a capture setup. They are primarily designed with broadcast in mind with a set it once approach or use a CCU. These are the kind of cameras that are often used on pan and tilt units at sports events and the likes so they are fairly high quality. (At least before the poor quality live mpeg-2 encoding i've seen)

The problems with using it for any type of production is more in the manual control. Without a CCU it is very difficult to change settings quickly. You have a handful of buttons on the back of these and thats it. But if you get over that they should be fine.

They are a little costly too and most are 1/2". From what I've seen more people tend to lean towards an XL H1 because of price and convience since it is already more of an ENG setup with HD-SDI.

As Keith mentioned, the 300 and 310 are designed as remote jobs for arenas and sport events, or inobtrusive worship events, but you can pedestal-mount them. Outside a very controlled studio, arena, or chapel, I can't see them being used, and haven't seen them being used. They are awesome in terms of output, we had one on the VASST tour and it was a blast playing with them.