If the key RebootRequired exists, this means the PC has a pending reboot. However, the values within this key are not the same pc to pc so I cannot set a value to scan. I also can't use (default) because it has no value set and therefore Lansweeper won't scan it. If Lansweeper can be set to simply check if a key exists and not check for values this would work.
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\WindowsUpdate\Auto Update\RebootRequired