The Sentinel on DVD? Maybe this year.
I followed a tumblr link (thanks, Mab!) and found this TV Shows on DVD article saying that The Sentinel will be released on DVD later this year. Note that although TV Shows on DVD cites a Visual Entertainment, Inc. press release, there's no hyperlink and I have been unable to find it on the web, and the VEI website does not have a future releases section. So, take it with a pinch of salt, maybe, but I'm going to be cautiously optimistic.