I don't see anything stopping you from the point of view of the vending machine, but you haven't explained how the payment occurs, or how the person paying knows the goods will appear at their machine (rather than some random remote one) or how the machine knows that the payment has actually been made before dispensing the goods.
If you want to set up an SMS based micropayment system then there are suppliers who can do this for you, but I can't really recommend trying to create your own solution for real-world use.