Rebooting when internet not in use

I have a wireless router/modem and PCs connected

wirelessly to it. Sometimes it gets into a

non-working state but turning the router/modem off

and on again fixes it. I would like to do this

once a day without having to go to other floors to

find out if anyone is using it at the moment. How

can I determine if the internet is in use? If anyone

else is using it at the moment I would wait for a while

and try again later.