you have two types of NuVinci, the one with automatic shifting is the Harmony. The other type is the Infinity. The Harmony is of course more expensive because it comes with an integrated computer.
http://www.nuvincicycling.com/en/products/overview.html
TBH, for hilly terrain, if you get a BPM bike, set your gear to whatever is your favourite, and pedal at your favourite cadence, as much or as little as you like, the motor is so flexible that it does the rest without whingeing. It's not the money, it's the simplicity (or complexity) of the way these things turn out in the field. No need for a heart monitor.