dancinglemons, this is practiced, slightly differently, in the maintenance of indoor plants. The 'grow pot' is placed in a saucer or similar watertight container. The technician pours water into the outer container and this water is taken up into the grow pot through holes originally placed for drainage.
The trick is to place just enough water so that the growing medium is completely dry by the time of the next visit.
I am impressed by how long some plants have lived under this type of watering program.

I live in SC just across the state line from Charlotte NC. For the past 3 years I've done basically what you're wanting to do with several modification ... thus, turning all my plastic pots into self watering systems. (1) I drill the side holes in four locations around the pot. (2)I put growing media in the pot up to the drilled holes. (3)I place several layers of DuPont 15 year landscape fabric in the pot, making sure to cover the bottom completely ... this stops roots from getting into to the bottom of the pot. An alternative is to skip the landscape fabric and use Smart Bags ... or any fabric bag. Works great! I've used it for pots from 12" to 24" dia and have planted tomatoes, roses, and all types of large plants (Russian Sage).

Some pots are sold as self watering containers ... they hold water in the bottom and have recessed areas in the reservoir platform to allow soil contact with the water (just like Earthboxes, Earthtainers, Garden Patch, etc.) With these pots, I simply drill the holes in the side of the pot, at the level of the reservoir. To make the reservoir larger, I have placed growing medium on top of the reservoir platform and then added the fabric cloth and growing medium or fabric bag. Drill your holes in the pot at the fabric cloth level.

Plus, I have a drip system hooked up.

Best of luck. It works for me

Tony