I just finished a really pretty walk through the Torres del Paine National Park in Southern Chile, all in the comfort of my atrium. I did this using the BitGym app on my 2017 iPad Pro. BitGym is quite different from iFit, and each has its pros and cons. I will try to contrast and compare the two programs.
iFit is part of the firmware of your exercise machine (a NordicTrak treadmill for me). The iFit program shows a snapshot along a trail every 3–5 s, and these images are taken from Google Maps Street View. They always look straight ahead in the direction you are going. So many hikes that seem attractive (e.g., around a volcano rim) show nothing of the main attraction! However, as you go along, and the path goes up or down, iFit changes the tilt of the treadmill. The user controls the speed.
BitGym works quite differently. It is completely independent of the exercise equipment. Instead, BitGym used the phone/tablet front camera to detect your bouncing (and thus your step rate) and uses this (sometimes) to change the speed of the displayed hike video. The videos are continuous, and gorgeous, and when you get to the hike objective, they stop and look around (yeah!). Thus, BitGym will work on any apparatus. However, it is up to the user to adjust the speed and tilt of the treadmill (or use one of the treadmill's built-in canned programs to do this). It might be a bit disconcerting for some users to have an equipment tilt that does not agree with that in the image.
BitGym offers two types of workouts without much documentation as to their differences.
The user selects a set of tours, and then proceeds as follows:
Coached tours have an actual coach who pops up on screen to tell you a bit about the place you are hiking through, and who exhorts you to exercise harder or easier, and puts up an arbitrary RPE (rate of perceived exertion) that you are supposed to use to adjust your exercise. The higher the number, the faster the scene moves.
I found that for the hikes I tried, the scene was moving at a running speed, much faster than my walking pace of ~109 steps/minute. In addition, the coached hikes have built-in music that I really found annoying. It has a metronomic clicking too.
The Low Speed/Nature tours react to your pace, and allow you to listen to the nature sounds as the hike progressed, for example, ocean waves, brooks, footsteps. As you progress, little text icons appear on the trail ahead and grow in size as you approach them. When the icon gets to you, a proper text box appears with some factoid about your tour. Another plus is that a single tour may contain multiple points of interest, so it is only a short walk to reach the destination. After a look around to see thye view, the BitGym tour switches to a new destination in the same area.
Here is a short video I made (without exercising) by bouncing the iPad up and down, to illustrate the low-speed tours with sound effects:
I have never tried it. If you write up a review here, I will publish it.