My DS 7 is still the occasional bedwetter...up until this spring he was an every night wetter. After talking with his doctor who said "no worries until he's 9 or 10, most kids grow out of it, but if you really want to do something you can try an alarm" and he recommended the SleepDry alarm we tried that. Interesting note here, we mentioned to the doctor that we'd tried limiting nighttime drinks and he said that rarely has an impact at all on whether a child is going to bedwet.
As other posters responded, the first 5-6 nights the alarm woke us, but not DS. This is expected and was explained as typical in the alarm literature. Each time the alarm sounded I would go pull DS out of bed, get him to the bathroom to "finish" if he needed to, then have him change PJs, etc. (the SleepDry alarm was great in that we could hook it up to a regular pair of underwear, but then put pullups on overtop of that so no changing bedding each night!).
Anyway, about day 5 or so when the alarm went off instead of having to drag DS out of bed and cope with zombie boy while trying to get him changed, I was meeting him in the hallway! He was starting to wake up when the alarm went off and knew that meant "get to the bathroom!". About day 8 or so he started getting up BEFORE the alarm and making it to the potty while still dry

For the next week or so he only had the alarm go off 2 or 3 times, after that he was alarm free for 4 weeks!
After he had been dry all night for the 4 weeks we stopped using the alarm, and he did pretty well for awhile, then started having accidents again. When that happened we started using the alarm again for about a week and that would be all it took to get him back on track. He does still have occasional issues, but using the alarm has really helped him understand the feeling of when he needs to wake up and listen to his body.
A few points before I end...
- My DS was wanting to stay dry during the night and really wanted to stop wetting the bed (we weren't punishing him at all, he just wanted to be more like his friends). Without DS being motivated I'm not sure the alarm system would have worked as well as it did.
- The alarm wasn't a full cure, DS still has nights when he doesn't stay dry, but he did go from EVERY night to maybe 1-3 times per month and he's getting better.
- It was very interesting to find out what time of night he was having the accidents....I expected it was early morning (like 5 am), you know he just "wasn't quite making it through the night". That wasn't the case! His accidents were always around 11pm or so. About the time he was probably in his deepest sleep of the night and therefore not waking up because he was in such a sound sleep. The alarm would go off once and after that one accident about 11pm, he'd be dry the rest of the night!
Anyway, not sure if I've helped at all, but thought you might like more info from a family who has used an alarm system and found it to be a positive experience. Having a bedwetter is tough, especially when they start getting to an age where the child realizes he's "different" then his friends. For me, just finding out that MANY other families have boys my DS's age that still have bedwetting issues was a relief and helped me not worry that DS was "abnormal".