There's, not much, I think. I did a security review a few years ago for a client, and couldn't find much. Helimission have a pair of Squirrels (certainly had, last time I looked) but they only do missionary work. And Assistance+ had a Bell 206 for medevac only.
Heliquip don't operate anymore, I think - their website
http://www.heliquip.net/madagascar.php still refers to ambitious plans for 2009, which is not a great sign...
I think there's an Allouette up in Nosy Be that does tourist flights.