Unless you use static IP’s or a DHCP reserved IP for your PI (or really, any Linux based computer) how do you know where it lives on your network? This might not be an immediate issue for you on your home network, but what if you take your PI with you to another network for some reason? It could also be used to simply let you know when a machine has been rebooted and is back on line..
Quite a few years ago I started using a VOIP provider called voipcheap. Aside from the very cheap rates they have for calling (including FREE calls to number of countries), I’ve also found them to be very reliable. Another feature they have is the ability to send SMS’s either via their website or via a direct URL that you can hit with with a few bits of info in the URL and they’ll send out your SMS for you.