Heart rate monitor sending text message

Hi
I am looking for advice on the best Arduino board to buy.
My project is to create a heart rate monitor that will send a text message when the rate increases by a certain percentage.

Can anybody advise me where to start?

Thanks
Lisa

You could tell us what kind of sensor(s) you plan to use, how they hook up (wired or wireless) and what kind of interface you want to use to ultimately send your "text message". If you plan on sending it over a smart phone then you'll need some kind of interface to the phone as well (wires or bluetooth). I assume this is just for personal entertainment and that you aren't actually building a medical device.

No, Im not building a medical device!!
I want to use a sensor that is attached to the body,maybe with velcro strap. The message is to be sent wireless, to smartphone.

Have you chosen any particular sensor yet? Any that you are looking at?