It can be done with a little help from community commons.
You can use the community commons storeURLToFileDocument to call the REST webservice. The answer is stored in a filedocument. After that call StringFromFile to read the answer in a string. Or import that XML document with an 'import XML' action.
Be careful: the constructed url with parameters must be url-safe. Java is needed for that.
There is currently no out-of-the-box or Appstore module available for this.
You could download and change the Deeplink module to execute certain actions instead of opening forms.