I watched a demo on the Eno board which is what we are going to have at the high school next year.  You can use them with your computer, with easy touch software, you can use dry erase markers.  The presenter even wrote on it with a sharpie and the later traced the writing with a dry erase marker (said you can use anything alcohol based) and wiped the sharpie off.

The board is also magnetic and there is a magnetic icon strip you can affix to the board.  You can use the pen that comes with it to access the functions and also draw or write on whatever you are projecting on the board.

They say they are not at all locked down, that the are just drivers and so the board is open to use with anything.  I don’t completely understand that but according to their website:

The eno board application runs on an open platform that works with existing software/operating systems, meaning education and business systems that have previous investments in software can still utilize applications

Here is a video demonstration
http://www.youtube.com/watch?v=SSLKGQEeags

Here is a link to software that can be used with it.
http://www.techedu.com/main_software.asp