I have used two different continuous glucose monitors (CGM) in the past year - the Minimed one and the Dexcom - and am currently using the Dexcom. I've written plenty of posts about the CGM on my blog (here's a link: http://sixuntilme.com/blog2/cgms/). The basic gist is that a CGM takes "blood sugar readings" from the interstitial fluid in your body and sends the readings to an external receiver, giving you a pretty good gist of what your blood sugar is at any given time and what direction it's going in. CGMs have high and low blood sugar alarms, so they're useful for detecting hypos in the middle of the night, as well as helping to determine whether or not your basal insulin/carb ratios are working out for you.
I wear my Dexcom sensor either on my arm or on my lower back, and I did a quick video to show how a sensor is applied. It's a tricky device to get used to, but knowing when I'm popping up too high, dropping too low, or just pinging all over the place has really helped me fine tune my numbers.
Are you going to be using a CGM full time, or just for a few days? If you're hooking up to one for just a few days, I'm guessing you may be hooked up to the Minimed system.
I hope this little blurb of info helps. I know there are a lot of other people on TuDiabetes who are either using CGMs currently or have used them in the past. Ask us anything, and hopefully we can help!!