I have used a similar and much cheaper principle for more years than I care to remember.
The purpose behind the system is; tomatoes have two sets of roots'feeders' at the top and 'water seekers' at the bottom something I think you already know.
The idea you suggested is a system to utilise this phenomina and there are a number of ways to do it.
1) the double pot system as you suggested.
2) Felt rings ( similar to roofing felt) filled with potting compost.
3) Bottomless buckets
4) Rings made from large diameter drainage pipes ( my method)
These effectively do the job of the top pot in the system you suggested.
With items 2-4 you sit the container on a bed of a material that holds moisture,e.g gravel and this is where you add water, this equates with the bottom pot in the system you mention.
So basically you have a two tier system.
In the link below you will see that I use drainage pipes sat on a humus rich bed to get my two tier system.
I sometimes take this a stage further and sit a plant pot in the ring (see pic 5) in particular I do it with cucumber as these are prone to 'neck rot' so applying water through this plant pot keeps the neck of the plant dry.
If I am growing my tomatoes in the greenhouse border I sink a 5" plant pot into the bed at the base of each plant and this gets the water directly to the water seeking roots,i.e. it is another variation of the two tier system.
I would suggest you look in to some form of DIY system first before going to the expense of buying double pots.
What comes to mind is the infamous black bucket that so many of the members of A4A use and comes free from the supermarket.
All you have to do is remove the bottom and voila.....you have the bottom pot and any old plant pot or cream carton is your watering hole.
http://www.thegardenersalmanac.co.uk/Data/Ring%20Culture/ring%20culture.htmlI leave my thoughts with you.
