Patch Planter isn't the first self-watering herb planter to cross our radar: that would be the AeroGarden. But where that product was an all-singing, all-dancing "kitchen garden appliance," Patch is a much more down to earth and affordable piece of design, and one that doesn't require a power supply.
Unlike AeroGaden, Patch embraces good old soil (or better yet, Potting Mix) as its growing medium. The planter uses a method of irrigation called subirrigation, which involves keeping a reservoir of water below the soil, from where water is absorbed upwards.
The planter is simply an open-topped Tyvek cuboid with a perforated shelf separating the growth medium from the water below. In the corner is a cylinder through which the reservoir is topped up, apparently as little as once a week in the early stages of growth, though every 2 or 3 days once they grow large. Whether this meets your expectation of "self-watering" will depend on your outlook. However, Let's Patch (apparently the makers of the planter, but also sometimes the name for the planter itself) claims this renders over- or under-watering impossible, saves water and maximizes yield overall.
Each Patch measures 12 x 6 x 6 in (30 x 15 x 15 cm), holding 4 liters of soil and 2 liters of water (0.9 and 0.4 gallons respectively). But Patch is really more of a bag than a box, folding down to only an inch thickness for postage.
Where this differs from AeroGarden is the lack of built-in lighting, which should be unnecessary for anyone with a bright patch in his or her home. Obviously this much simpler design makes the Patch the more affordable option. At the time of writing a second-tier Patch can be secured for a US$33 sum, rising to $38 when that tier is exhausted (or if you're in generous spirits).
The Kickstarter campaign video below gives a few more glimpses of the Patch, and should serve to mightily confuse you regarding the product and company branding (it did me, anyway).