It is about using a means of practical payment, universal and safe for accessing to contents via Internet, without having to resort to credit-card systems, less adequate when working with small sums of money.
For this, users need sending a message to a short number, and then the system will provide them with a password to access the content or requested file.
The page administrator only needs to add a short "script" (source code) in the access page that we will provide him, which carries out the function of validating users and rendering useless the just given password.