Hi, I have preordered the DecaGear and am a member of the Deca Discord Cannel, but skipped the DecaMove so far because of not having too much use of it. But it is definitely very interesting. It should work with everything that uses the VR controllers to aim with a weapon/hands plus the head to look around and to move in the direction you look, with no need to add anything to the game itself. This genious idea is done by constantly measuring the angle between head movement and hip movement and constantly substracting the difference from your controller input, so that you can virtually move the head independently from your look/move direction.
In THEORY, this should work in VaM out of the box, too, but so you usually don't move in the look direction in VaM like you would do in a 1st person shooter, there is IMHO nothing useful the DecaMove can do. It is NOT A TRACKER in the usual sense. AFAIK it can't recognize it's position in full 3D space, but only can measure the angle between DecaMove and Headset. If it could do so, it would be indeed a much bigger sensation as it actually is.
I would be glad if I would be prooven wrong by someone else, but as far as I have understand how it works, I unfortunately can't see any benefit for using it with VaM.
But IF I am wrong or if there would be a mod or something, then I am sure MeshedVR would add any necessary support to VaM, as AFAIK him he likes all new gadgeds the same way we all do.