Participants can be instructed to let them sign up to a survey by texting a key word to the project number. Then automatically the new respondent is included to your survey and they will instantly or in accordance with a pre-made schedule receive the text message question in the survey. The participants then will include themselves, hence have accepted to participate.
You can prepare a survey with no participants created, however when the participants text a keyword to the project number they will be automatically added to the survey and will receive the questions.
The keywords could be “go”, “start”, “yes” or whatever fitting your project.
The keyword should be simple in order for the participants to sign-up easily. After signing up, the programme can be set-up, so a message confirming the sign-up is send back to the participant.