We sort of do something similar, but instead of using their network, we use our everyday home wireless network. We use an outdoor wireless IP camera that cost about $95 from Amazon. We have a static IP address through our internet provider (Skybeam) which costs $5/month. Plug in the static IP web address from anywhere, and voila! I don't know what this camera and service costs, but when I looked into marestare and some of those other services a couple of years ago, I couldn't believe how cheap getting our own system up and running was in comparison - and pretty user friendly, too, which was important because I'm a techno-idiot.
Our camera is waterproof and has night vision, and we check in on it all the time; way more than we thought we would. Ours is also positioned so that we can swing it around and it will focus on our paddocks and pastures too. It is perfect for foaling; the night vision capabilities on it are such that it can be pitch black out and the picture is clear enough to easily see what's going on, so we don't have to leave lights on all night.