Twilio will allow you to send SMS messages from your Hubitat Hub.
Visit twilio.com to get an account and that gives you an Account SID and Auth Token (long long random letters and numbers.) and a unique phone number.
On Hubitat, create one (or more) virtual device(s) and assign it the Twilio driver.
Paste in the two Tokens from creating a Twilio account. Save.
Select the Phone number to send from and type the phone number to send to. Save.
Use the Twilio device(s) in Rules and Apps to send notifications.
1. Sign up for a Twilio account at twilio.com
2. Go to https://www.twilio.com/console to retrieve your Account SID and Auth Token
3. Authorize a phone number to send messages to using https://www.twilio.com/console/phone-numbers/verified
4. In Hubitat Click "Devices" then Click "Add Virtual Device"
5. In Device Name enter the name of the device, ie "My Twilio Device" for Type select "Twilio Notification" then click "Save Device"
6. The device details page will open and you will enter the Account SID and Auth Token from Twilio into the input boxes and then click "Save Preferences"
7. The page will reload and you will be given the option to select the "From Phone Number" which will be the same as the one listed on the Twilio Site and you can enter one of the verified phone numbers that were entered on step 3 then click "Save Preferences".
8. The device is now able to be used in Apps as a notification device or you can use it manually by entering a message in the Device Notification box and clicking the button.