Is there an application with a graphical interface that can allow me to "see" devices on my network?

Try Network Magic by what was once PureNetworks, but has since been purchased by Cisco. It alerts you of intruders, includes both ip and mac addresses, and lets you know when anything joins your network, invited or uninvited.

But watch out with that software! I believe it now stores your report on it’s website instead of on your pc and part of that report is the websites visited by your computer. Do you want that info to get out?

I turn off reports. I find them neither useful nor necessary.

I’m not sure turning off reports stops their website from getting the info.