The states already keep child molesters on a short leash by requiring them to register. Not registering is a Felony.

Murders/Rapists are usually Class A or B Felony which means you go away for a long time or go away for ever.

If released I am not opposed to RFID or ankle band tracking. Removal of which results in permanent incarceration. If you reoffend and are found guilty in a subsequent trial. You get fast tracked to the needle, firing line, gallows, whatever.