if all one is concerned with is having phone service in case of emergency, another option without having to buy a local SIM or pay for an international roaming plan, is just using your US phone and paying the full international roaming rate...looks like AT&T is up to $3/min. now for the Caribbean, which admittingly is pretty steep....but personally, since we don't actually PLAN to use our phones for local calls, we choose not to pay for any additional plan or buy a SIM

we use WiFi (calling, texting, email, FB) for all planned communication to the US

Note: for those considering the AT&T Passport plan, remember that in addition to the $40 monthly fee, you will also pay $1/min for calls