I was going to buy something like this so that I could pocket my pro during the summer. I usually like lighter t-shirts etc and having something on my waist looks so dorky. It's easy to concearl when you're wearing sweaters/jackets most of the time during winter.
That, and my girlfriend always gives me that look of "oh god, please take that off :P"
Then I give her the look of "I understand, because it does look dorky, but your purse doesn't fit in my car."