to track limb movements you need EMG attached to your legs and then to a recorder. Then a sleep tech certified in scoring must review the results.
A board certified sleep doctor can get you home devices to track periodic limb movement if necessary.
Acti-watches are the only devices that you might be able to get "accurate" sleep(not limbs)tracking. They're expensive and you need to buy analysis software to view results. I would not waste your money on any publicly available device- they wont get you the data you want.