If you have electronic device on you, you are leaving a trail behind, like footsteps. Is it creepy or illegal to follow or collect those [footsteps]? I telecomm

If you have electronic device on you, you are leaving a trail behind, like footsteps. Is it creepy or illegal to follow or collect those [footsteps]? I telecommute (* ) and easily check if people are in or not by pinging their computers (you may check for visibility of samba shares) - they have no expectation of me knowing they are in or not, but by no means i see this less creepy then your instant messenger of choice showing you as online and me checking. It is increasingly becoming bigger and bigger responsibility of ours to stop leaving these traces behind. * i have never been told, but can easily imagine my VPN connection logs (server side) can be checked for when i logged in/out (not that they could even imagine i get in also via ssh/port forward through another box, when the VPN is down due to admin negligence) so i have no expectation of privacy there either.