Here's an eye-popping interest rate: 5.1 percent. You can earn that much in a plain old savings account, if you are willing to jump through some hoops.

Union Plus, a group described by its leader Leslie Tolf as "AARP for workers," has launched a low-fee prepaid Visa card tied to a high-yield savings account.

The prepaid card offers an alternative to traditional checking accounts and to high fee check-cashing establishments frequented by the unbanked.

As I've written in the past, prepaid cards have been growing in popularity, but they can be riddled with fees for everything from depositing money to taking money out. However, some institutions have listened to consumer outcry about excessive fees.

Union Plus is one of them. There are several ways to add money to the card without a fee. Plus there are no monthly maintenance fees so long as you deposit $500 per month on the card (otherwise it's $2/month), and no fees for activation, statements or customer service.

The main fees are for ATM withdrawals ($1.50) and bill pay ($1).

But what really makes this card appealing to me is the surprisingly high interest rate offered on a linked savings account, designed to entice non-savers to sock money away. 

Up to $5,000 in deposits will earn a 5.1 percent APY so long as the prepaid card is open and has a positive balance.

Bill Hardekopf, who runs lowcards.com, a site that tracks all forms of plastic for consumers to compare, says he doesn't know any other savings account that pays that much.

The maximum you can save in this FDIC-insured account is $10,000, and any amount above $5,000 earns just 0.10 percent.

What's stopping me from opening the prepaid card just to access that sweet savings account?

Nothing, I was told. I can load money on the prepaid card and transfer it to my no-fee savings account. When I want the money, closing both accounts will trigger a check sent to me.

One issue: It looks as if the direct deposit must come from your paycheck, not from transferring funds from another bank account.

If you're sick of rock bottom rates and can handle the hassle-factor, it's an option.

You can sign up at www.myunionprepaid.com if you are the member of several unions. Otherwise, you can list yourself as a member of "Working America" to qualify for the card.