It's just a prepaid debit card that you can load using various techniques mentioned above. You can also deposit checks to it via mobile deposit.
I have 5 automated transfers of $200 every month. I do this on the 3/5/7/9/11th of the month. On the 15th (or so), I log on and send a bill payment to my mortgage company for ~$950 ish. I let the remainder sit there until I have use of it or pay it towards paying a credit card bill. If you get aggressive, you can buy SOME prepaid debit cards from brick and mortar stores with your credit card, and then load the debit card to your serve at a local walmart. Some walmarts wont allow this, but others will. Mine do. You'll pay an activation fee for the debit cards, but typically, the cash back is higher than the fee. For example, I can buy a $200 visa gift card from Staples for $206.95. I then load $200 to my Serve account. I then pay off a different credit card's bill for $200. In a month, I'll have earned $10.35 in "points" from my debit card purchase. That means a profit of $3.39 per $200 debit card. Since my local Walmart has a self-service KATE, I can load 9 $200 cards and make $30.57. Total time from office store to Walmart is maybe 30 minutes. Just whatever you do, always start small. Unexpected fees are much less annoying when it's small.