My experience with iPad vs. many posts in the forum regarding CrystalSky pushes me to recommend against CrystalSky. It's my understanding that it runs Android, which has not been as reliable as iOS. I have used 4 iPads with a half dozen DJI drones over 10 years and have experienced not a single failure. CrystalSky can't make those claims. That said...
If you're just flying for fun and your flights aren't "mission critical," then go for it. My situations were always mission critical, so I steered clear of Android offerings, which included the CrystalSky.
Disclaimer: I am no Apple Fan Boy, but I recognize when a tool works as it should. I give credit where credit is due and these iPads have been 100% reliable. Very few tools can make that claim. Any issues were with DJI software/firmware, which I worked through by hacking the original programs.