There is no built-in function in splunk to send text messages as far as I know, so you'll have to rely on a third party for that - my first find was Tropo, for instance, but you'll be sure to find what you need with google.
To use something like this from a splunk dashboard, I could imagine it's as simple as adding an <html> tag to define a button and call some javascript when it's clicked. You could also pass any search results to js either via tokens, from a drilldown action or from the search directly.
