I'm sitting here looking at 2 ET-73 displays right now- one probe for the smoker temp and 3 probes going into a hunk of corned beef, one probe per shelf of 3 hunks on each. They're sitting side by side outside, and the displays are side by side inside and the readings "know" where to go for each of them. Pretty cool. All you have to do is turn on the receiver, turn on the probe unit and wait a couple of seconds for them to talk to each other. Then repeat for the 2nd one.
Batteries last a long time in them. Technically the probe part is water resistant since it has rubber gaskets but I haven't checked that yet.
I like them so well that I got my brother and father one for Christmas! All four have worked without any problems, and none of them have broken since then. I wish the probe cords were a bit longer sometimes, but I haven't wished hard enough to go out and get the 6' cords that are available for them yet.
There are some other good ones out there too, but for the price (look around some on EBay, Amazon and at yardandpool.com - mine were cheapest at yardandpool back then; I just checked and they're still $39.75- shipping for 2 was like $9 for standard) I like these a lot.