https://www.mesh.com/welcome/default.aspx Install this on all your machines and make sure you have logged into machine and then locked it. Live mesh needs a windows live id. You may convert any of your email-ids into Live id. And then live mesh system tray applet will show all your devices along with a connect to device if machine is up.
Now, comes the dirty part. Windows 7 has nice power saving features designed to help an average joe save power. But, technical people cannot afford to think about power savings and be productive at the same time. So, we will tinker with these settings.
Start -> Control panel -> Hardware and Sound -> Change when the computer sleeps (Control Panel\Hardware and Sound\Power Options\Edit Plan Settings should be the title of control panel page).
Change "Put the computer to sleep" to Never.
Start -> Control panel -> Network and Internet -> Network and sharing center -> Change adapter settings -> Right click and Properties -> Configure -> Power management -> Uncheck "Allow the computer to turn off this device to save power".
Its bad to turn off all these power savings features, but that's the way if you need to access this machine anytime. There are some options related to LAN / WAN wakeup packets, but I could not explore these till now, so the above one seems easier choice.
For home machines, one may need to buy UPS like APC Back-UPS ES which allows auto-shutdown of machine. this way, machine can be left running at home and connected from office. If there is extended power cut, UPS will turn off machine to save from problems. In this case, Modem & router too should be connected with UPS supply.