for what i understand depends on what kind of restraint you are using, if is for a child or for adult, if is the 4 point bed or seat (used for police and psych units). there are multiple types for multiple body sites, restraint hands in semi-conscious, etc.
now you have to report (document) every 15 min. (observation) and let patient free (physical) every 2 hrs for rom and check circulation (and document). and 1:1 sign offs are every 30, basicly as rach10388 stated.
According to Saunders (p. 181)
Assess skin integrity and neurovascular and circulatory status q 30 min and remove the safety device at least q 2hrs
According to Fundamentals ATI (p. 106)[FONT=StoneSerifStd-Medium][FONT=StoneSerifStd-Medium]Assessed - Including neurosensory checks of affected extremities (circulation, sensation, mobility). These checks are usually done at least every 2 hr.[FONT=StoneSerifStd-Medium][FONT=StoneSerifStd-Medium]