There are ways to do this much more simply and more compact as long as you’re willing to go with just one cellular network at a time and keep an eye on it. No backpack required – just your pockets, or a pocket of the backpack/camera bag you already use.
The truth is you should have all 4 cellular networks at your disposal when possible – there are places where only one network works that well, and it could be any of them.
This cellular bonding technology can be essential for video, but can be overkill in many photo applications. It still doesn’t hurt – as long as his solution is compact enough for him it’s great, but competitors could do almost as well on a shoestring (with zero software development or custom hardware) …
Started out doing photography at the age of 6 using an uncle's old 1940 kodak brownie box camera. At 15 years of age, I decided to buy my very own 1975 Praktica SLR camera. I now shoot with a Nikon D850. I do unpaid TFP and commercial paid work.