Accessories
I can't find any way to look up invoice pricing for the individual options - I'd like to at least have a ballpark of what I should be aiming for when I go in to talk to them.
Edmunds.com has a way of showing invoice on individual options. Just search for the car you're looking at, then click "build" at the top of the page. Click "build and price", and you can choose individual options. At the end it will list a breakdown for you, each option will have an invoice, MSRP, and Edmunds "true market value" price. I can't speak to if the last of those is more accurate than KBB, TrueCar, or any of the others, but I did read several well-known publications mentioning that Edmunds' pricing tends to be pretty accurate as far as what the market is giving.
I got parking sensors on mine. A lot of people said that the rear camera is fine, but I like being able to keep my eyes on the front of the car while being able to listen to how the back is doing while I'm parallel parking. If I end up hating the sensors, oh well, I can disconnect them.
7eregrine is absolutely right about not getting Mazda Mobile Start, the app-based remote start. However, the remote start with the fob is available, at least according to Mazda's website and my dealer. I don't think it has some of the same features (lock/unlock, GPS location) that the app does, but it'd be less frustration and you don't have to keep paying for it every year.
Something to keep in mind when considering options on your new car is the warranty. If you get an accessory at the time you buy your car it will be covered by the three-year new car warranty. If you drive off the lot, drive a block down the road, and come back and say "you know, I think I want the mobile start/parking sensors/whatever," it's only covered by the 1-year accessories warranty. So if you think you want something, and you have the money for it now, get it now.
Good luck!