Self-leveling alternatives to gypsum concrete (Gyp-Crete, Pyrofill, Securock) over OSB?
We generally don't recommend self leveling alternatives on a substrate other than concrete, vibrations over time can affect their stability. Best option is shims and plywood.

That being said, you're asking for a self leveling option. Your best bet would self leveling concrete, you'll need to pay attention to the substrate requirements, it says it accepts certain wood based substrates, however compare their requirements to your situation. 

like:
http://www.lowes.com/pd/MAPEI-Gray-and-Silver-Indoor-Floor-Patch-and-Leveler/1180155

Also, most of these 'concretes' are safe for electrical radiant flooring installations.