Event-based SMS marketing is rarely used for mobile app and web app marketing. But there's no reason to avoid it if you do it right. 95% of text messages are opened within 5 minutes. If you get your web app and mobile app users phone numbers with permission, sending an timely, personal, and relatable trigger-based SMS to help them use your app will be appreciated.
For more user onboarding hacks for web apps and mobile apps go to http://autosend.io/how-to-onboard-users-email-sms-push/