Our foaling record is not much different from yours, even with a cam, MareStare and some type of sensor on the mare. We used the foal buzzers first (cost about $55) with a baby monitor and the camera, and that is OK as long as you stay within range of the baby monitor. For about ten times the price, I now use the EquiPage system with pager (rather than the phone dialer) and feel it is worth every penny. The pager will work anywhere on our property and alerts me when the mare goes down. A quick look at the camera - or the mare - to see if it is for real or not. Of course, I am still a nervous wreck, but this and Mare Stare is a HUGE help.
The other thing about the baby monitor system, is that you hear ALL the barn noises, including those made by horses NOT on camera. I had to go out to the barn several times in the night to see who was munching hay at 3 AM (Ruby) or who was playing with their stall toys (Buckshot). And all the horses get to hear the foal buzzer too. Neither is the case with the EquiPage, so everyone can sleep better.