I find this to be a very useful device! Though the technology has been here for a while now, it wasnt until the threat of hurricane Irma did i decided to buy one.
Thankfully my power never went out when the storm came but i still had thr interest to use it when I go back to work.
For someone that uses their phone alot, my battery % stays at 100 the entire day. Even after I made it back home and comfortably relaxing in my home.
Now when its time to recharge the battery charger, i can keep it connected to my phone as the battery charger is charging from one of my walls. This is fatastic! I no longer worry about my battery running low.
Now there is a con but I think its manageable. The battery charger and the phone linked together makes putting the phone in your pocket a bit difficult. Even talking on the phone with the phone up to your ear becomes a bit more difficult. And imagine while texting, you have to hold both the charger and the phone.
Now obviously you can disconnect your phone and use it, then connect it back when the phone is not in use.
Until better technology comes to light, I say it's well woth it investing in a strong battery charger.