Hammersly, here is the company I went with after considering others. I am in NO way affiliated with them, but CAN attest that their customer and tech service are extremely helpful during all phases of design/buying AND installing their products.
Shipping was extremely quick and there was always someone to answer my questions knowledgeably. I used their 30" wide heating mats--http://www.warmyourfloor.com/suntouchmats30inchwidths. aspx,
which can be reconfigured to many different shapes, but I believe if you are more adventurous and careful, you can buy and install just the wire for much less--http://www.warmyourfloor.com/warmwirethinelectricheatingcable. aspx
This is the programmable thermostat I used--http://www.warmyourfloor.com/sunstatproprogrammablethermostatlcdwhitenew120240v. aspx
Good Luck... it's definitely a NICE feature, and like Kenny61 pointed out, also a selling point.
PS--our 1/2'' thick limestone floor takes about 30 minutes to heat up from 60 to 72, but it will be different for different types and thicknesses of tile material, subfloors, substrates, and insulations under the flooor. The guys at SunTouch should be able to give you an approximate idea, but if you buy the multi-event programmable thermostat, and generally follow a schedule, then it doesn't really matter. .