We have recently developed a plugin to add an email address to a list and trigger an auto responder using Campaign Monitor.
You can simply setup a list in Campaign Monitor and makes sure the keyword matches your list name and when somebody texts in KEYWORD email@example.com the email address will be added to the list triggering the auto responder.
Use the following URL in the Send Response to URL field in keyword setup.
Where the access key is, enter your Campaign Monitor API key, which can be found in your Account Settings section of your Campaign Monitor account.
Example: Try out this recipe delivery solution.
To get the ingredients and recipe SMS the word BEEF and your email address to 0459 333 444 eg. BEEF firstname.lastname@example.org
This is displayed at POS and immediately texts the person a list of ingredients which they can then shop for. At the same time the recipe is emailed to their email address to access when they get home.