Summary

The SMS destination number can be pre-filled though this not the best UX without a pre-filled message, as once the user is in the message app there are no more visible instructions, even if instructions are given within the ad unit.

Device support is not wide enough to reliably pre-fill message text for all platforms.

Compatibility

Capabilities that are not supported by all platforms are possible but will reduce your reach.
  Android 4.4.4 (S4) Android 4.4.4 (Note 2) Android 5 (HTC One M7) iOS6 (iPhone 4) iOS7 (iPhone 5) iOS8 (iPhone 6+)
Pre-fill SMS destination Y Y Y Y Y Y
Pre-fill SMS body copy Depends on the user's SMS app Depends on the user's SMS app Depends on the user's SMS app Y N Y

Version distribution: Apple version statistics, Android version statistics

Test Unit

'sms-msg-test' in customads