Hi Guys,
Im a father of a 5 yr old boy and got another one on the way (Feb-09). I remember when both my wife and I were 1st time parents we had a monitor that had a temp indicator and an alarm (when too high) on the parent handset - which went on almost as soon as the monitor was switched on.
My son was born in the summer of 2003 - that boiling summer which we just don't get that often. What we found is to take the temperature as a guide but do not let it worry you too much. We could not control the room temperature that much other than getting fan's blowing into the room, but it was just ciculating hot air around. My best advice is, don't over dress them during hot nights. You as parents will get a natural feel for how much clothing the child needs. Also, out parents never had gizzmos like this are we turned out well (well I hope so

)
Regards,
Sunny.