E.L.
I have one and it has proven to be a very accurate and valuable tool for us. It lets me know when to calm down, when to monitor an ear or when to call a Dr.. The 2 times that it said to consult a Dr., it was correct.
We got ours dirt cheep ($9.99) during an Amazon special (we actually bought 4 and gave them as gifts) so keep an eye on some handy websites:
atomicdeals.net
dealnews.com
slickdeals.net
woot.com
and you may find a good deal!
E.