Well, the press release regarding the Sentinal was dated 1999, and there's little more mention of them. Apparently they were started in '94, and managed to raise about $28mil in capital; It seems like they were on a good path for early video conferencing systems... they were publicly listed on NASDAQ but lost their seat in 2000 because they weren't meeting their minimums; despite offers from others to buy the company as they were dying, they chose to just shut their doors and fade away.
If you want to play with it, there's a cheap one on ebay right now!
http://cgi.ebay.com/C-PHONE-SENTINEL-CFON2...1#ht_1050wt_883