I think Bank of America has had a program like that for a while. Any purchases from your debit card are rounded up and sent to the savings account. I don't think it works with credit cards. Haven't really looked into it.
I don't know that it's a necessary application, but if people have trouble saving money, it could be a good tool for them. One potential negative side (and you might even see it in the app's marketing) is that it could encourage people to spend more because they will be "saving more." People could end up in a lot of credit card debt while trying to save. Uh oh!
Also, is that considered a cash advance on the CC, or is it a purchase of a savings instrument? I know my card has different limits on cash advance.