Best Buy again offers the Powermat Wireless Charging System for iPhone 4, model no. PMM-1P4-B19, for $19.99 plus $3.99 for shipping. (In-store pickup is also available.) That’s tied with our expired mention from earlier this week and the lowest total price we could find by $7. Sales tax is added where applicable. This system includes both the charging mat and iPhone 4 case.