Fixed the features page, thanks.
Yes, you can manipulate the IK target at runtime. The target is just a bone, so moving it is easy. The IK is applied at runtime, so you changes will be visible. Eg, if your character is standing on an uneven surface, you could move the IK target for the feet up or down and the legs will bend or extend so they will be standing exactly on the uneven surface.
There will be some fancy Unity features soon. Take a look at what Mitch has been doing!