My Weboost unit works pretty well as long as it is optimally installed and if there is at least some signal to amplify. In fact, I am in northern WI right now and I have 0-1 bars on my phone without the device and no cell service. When I flip the switch, it goes to 2-3 bars and I have pretty good internet access.
You can also accurately measure the decibel signal strength instantly if you put your phone in Field Test Mode. My decibels improve right now by about 40 db with the unit on. I have also used the Open Signal app on my phone to measure upload and download speeds with and without it on and it clearly works. I did used these 2 tools when I installed the device in my van to make sure the outside and inside antennas were in the optimal locations for best amplification.
https://www.weboost.com/blog/how-to-...-on-your-phone
The one problem I have with it is that it runs hot and has a fairly high amperage draw so I use it a little sparingly if I am trying to conserve my batteries. Of course, they are also not cheap and may very well not be worth the cost for many people.