A quick search here should turn up a few threads on the subject. The short version is yes, you can make some work.

I'll add that I got some cheapo BMX tensioner to work on a pretty sketchy setup today. I swapped out my 16t cog on my rain bike for a 15t and had to drop a link. This left the axles about halfway out of the dropouts. I was understandably concerned and didn't have a chance to get a half link (news flash: Kip, owner of Boston Bicycle & Cambridge Bicycle has never heard of a half link, Broadway was closed, Community was out) so I grabbed that BMX tensioner I had floating around. It didn't have a short enough reach to use for the project I originally got it for.

Anyhow, fit it with the threaded shaft on the outside, then turn the little slotted block that the track end normally sits inside of so that it's braced cross-wise on the back of the dropout, thread it down, and voila: cheap tensioner for a horiz dropout.

Tonight I bought a half link at Broadway though so I can ditch that ghetto fabulous setup.