Art of Networking
Part Art. Part science. All fueled by caffiene.
You TL;DR? No it's really, really not. There is a WiFi booster as in the physical hardware piece of kit but there's nothing a phone app can do to "boost" a wireless signal.
I was out last week doing an install. The wife came down as well because it was pretty routine and meant a long weekend in a new city afterwards. Only problem was the hotel wireless was... well it was just easier to use a phones data signal.
Somehow in the space of time it took for me to get a quick workout in the gym she'd managed to find herself on the app store looking for WiFi booster apps. She does some things very, very well but tech just isn't one of them. So she spends $20 on things promising to "boost" her wireless. She even thinks she succeeds when one app tethers her data connection and she puts half an episode of Breaking Bad through her phone data before I come in and point out the data signal going beserk.
There are some uses to a mobile phone app for improving a wireless signal. Some. Not a lot. And nothing a desktop application can't do better. But they can, for example, tell you which channels and frequencies are busy in the area. They can (very roughly) work out the location of a router so you can move closer towards it or point a directional antenna. But there is physically nothing software can do to create a wireless signal where there was none before.
The one exception to this can (rarely) be the firmware. If you update the firmware on your router or phone (or the driver for your wireless adaptor for a laptop or desktop) then the software developers/manufacturer might of found a better way for the device to use the hardware. This isn't common but might be worth a go you should have these things updated anyway for security.
I love how the Android market makes everything so easy to work with but I hate that it gets full of rubbish like this. Fancy charts and fake promises but no actual results - not that it stops them charging you. So no, wifi boosters are not a thing. They can create a wifi signal but the device only has one wireless card which means it can't connect to another network while doing so. So any data shared is coming from your phone.
Not all doom and gloom though. There are plenty of things you can do to improve your wifi signal. Whenever we install a wireless network in a bigger office we generally have to look at this to make sure there are no wireless dead zones. We actually got a call back once because the toilet in a janitorial cupboard couldn't get on the wifi once.
We don't suggest people get pointless apps on their phone but instead we install actual wifi booster devices. Nothing in common with the apps other than the name these devices are actually built for this kind of thing. They connect to a wireless network the same way as your device would (although you can position it closer to the original wireless router) and then creates another signal. Packed with amplifiers and antennas it gets a strong signal from a distance and the new network is even further. Connecting to the new network gives you access to anything the original has from devices to an internet connection. Wifi boosters are our go-to when swapping the channel isn't enough.