The house took me seven years to build so by the time I was ready to actually tile the room they had come out with some heated floor systems for warming tile floors and I splurged and went with a single ribbon system instead of the mat system since my floor was oddly shaped.
I got it on EBay and can't remember what I paid but I think it was around $600 for the entire kit including a thermostat that keeps the floor just a few degrees above the room air temp. You can get bigger systems to actually heat the floor but that seemed to expensive and unnecessary in Florida.
Step 1: Getting Started
I went as far as making the exact finished dimensions in a manner that minimized the amount of tiles I would need to cut. This might not be that big a deal if you're just doing one room but I did all my bathrooms, hallways, entranceways and the kitchen floor in tile so I had to put down about 1700 square feet of it. A little planning ahead goes a long way if you're just in the designing phase...
I used backer board for the walls of the masterbath and the heated part of the floor but in the rest of the house I did mudpans which if I remember I'll do another Instructable on and link HERE. (http://www.instructables.com/id/An-Alternative-to-Using-Backer-Board-over-Subfloor/ )
I chose not to heat the base of the shower itself because I didn't see anyway a low current system could keep up with water flowing over it's surface and I had to line the subfloor with a sheet of shower pan and didn't want to pierce it with the cable guides and I was also worried about running the heating coils up against the rubber. I didn't see much point in heating the floor under the vanity either so I chose the size of the heating strip accordingly, which was about 45 square feet.