Location sharing by SMS was also discussed here:
https://help.locusmap.eu/topic/22460-share-location-via-sms-periodically-or-at-the-push-of-a-button#comment-89401
Good luck !
https://help.locusmap.eu/topic/22460-share-location-via-sms-periodically-or-at-the-push-of-a-button#comment-89401
Good luck !