Yeah, first off you can buy a multi-meter at any place that sells electrical stuff for less than $30 and it will do everything that a Gamcheck or Gamcheck Jr. does... it's just not as convenient.
Gamcheck can check for power on one end, check that your lamp is good on the other end, and if you plug a cable into both ends at the same time it will tell you if the cable is good. Gamcheck Jr. only checks power. Gam Lampcheck only checks that your lamp is good.
I suppose you could try plugging one into each end of a cable to fake the cable test... I don't know how they are wired so I don't know if that works or not. Anybody know?
OR for about $15 you could get a basic continuity tester, a basic power tester, and a set of alligator clips and you've got it all right there.
I've never owned any of them because like I said, I can do all that and more with a multi-meter. I wouldn't get the most basic one... but something in the $30-$40 range will handle everything you need and more.
Gam is not selling a magic product. They are selling convenience. If you are hanging 40 feet in the air from the grid, you don't want to take the time to get the alligator clips hooked up to the continuity tester and hold it all just right. You want it to work now. If you can pull the instrument down and put it on the bench easily, then there's no real need for any of the Gam test products.
What you DO need is a pin splitter. There isn't a way to fake that safely that I've found.
Nope, you need power on the line to test a cable, the lamp check does not put enough power on the line, nor does it put anything on the ground. Having a multi meter is nice and you should have one, but nothing beats the speed of a set of checkers. I usually run the lamp check through every fixture on a meat rack before it goes in the air (also helps to get all the lamps replaced in the house before I have to pay for them). Also, with a power checker you dont have to remember how the plug is wired, it tell you right there. On top of that, a multimeter does not put any resistance on the line where a power checker does. If there is no resistance on the line the dimmer will put out power, so a multimeter will tell you a circuit is "hot" when it is not.
I don't think that resistance in the line affects how a dimmer operates. If the load affected how much power the dimmer puts out then twofering would be a nightmare. Dimmers should always output a relatively constant voltage for whatever percent they are dimmed to. Plus, if there was no resistance and the dimmer put out power it would be quite dangerous. If you had a graphing multi-meter you could see the gating action of the SCR, but a regular multi-meter will be able to measure voltage just fine. I think that if your dimmers are reading as hot on a multi-meter when they are supposed to be off you ought to have them serviced.
As everyone else has been saying, the GAM Check full size is the better deal, the GAM check Jr.s are all over priced for what they do. The question is how specific of an answer are you asking from the tester to give you. If you want to know if the hot/neutral/or ground is cross wired or shorted only the GAM check can tell you that accurately.