You are going to need more than 1 Tbone. You wouldnt want to skip the probe in the meat, how else will you know when its ready to pull.
For example 3 different pork butts all weighing roughly the same will be finished at different times. (just the way it works) There are so many factors to consider that it really is a good idea to have a thermometer for each piece of meat that you are cooking in addition to 1 that is dedicated to measure the grate temp.
I just picked up 2 more from of all places...www.qvc.com
. I found their prices to be 10 bucks cheaper than other online retailers. Of course you can usually find good deals at HD or lowes or even bed bath and beyond. Get some good quality thermos because they really are a very important part of a successful smoke.
Hope this helps.