If you have the SPG Amex, you can download Square and send yourself payments by swiping your SPG Amex.

The fee is 0.275% per transaction, which translates into 2.75 cents per point. Further, you can theoretically halve the cost per starwood point by using the monthly single-fee option from Square and charging $20,000 in one month (20,000 points for a fee of $275 = 1.375 cents per point).

Hope that helps!