Ever since VR Objects were made available, the SDK has had ovrTrackedDevice_Object0, ovrTrackedDevice_Object1, ovrTrackedDevice_Object2 and ovrTrackedDevice_Object3. It's also possible to bind two touch controllers as VR Objects (I haven't tried more than 2 yet).
However only ovrTrackedDevice_Object0 works, and if two controllers are bound as VR Objects then they conflict with each other, alternating which is active, making both unusable until you remove one of them.
Will all four objects be supported in the future, or is one going to remain the limit?