In the past I used to pay for an email->SMS gateway, which was used to alert me about some urgent things. That was nice because it was bi-directional, and at one point I could restart particular services via sending SMS messages.
These days I get it for free, and for my own reference here is how you get to receive free SMS alerts via Orange, which is my mobile phone company. If you don't use Orange/EE this will probably not help you.
The first step is to register an Orange email-account, which can be done here:
Once you've done that you'll have an email address of the form email@example.com, which is kinda-sorta linked to your mobile number. You'll sign in and be shown something that looks like webmail from the early 90s.
The thing that makes this interesting is that you can look in the left-hand menu and see a link called "SMS Alerts". Visit it. That will let you do things like set the number of SMSs you wish to receive a month (I chose "1000"), and the hours during which delivery will be made (I chose "All the time").
Anyway if you go through this dance you'll end up with an email address firstname.lastname@example.org, and when an email arrives at that destination an SMS will be sent to your phone.
The content of the SMS will be the subject of the mail, truncated if necessary, so you can send a hello message to yourself like this:
echo "nop" | mail -s "Hello, urgent message is present" email@example.com
Delivery seems pretty reliable, and I've scheduled the mailbox to be purged every week, to avoid it getting full:
|Username||Your mobile number|
If you wished to send mail from this you can use smtp.orange.net, but I pity the fool who used their mobile phone company for their primary email address.