This one was actually really nice for a while.
It cleans the strings almost as efficiently as lemon oil and a cloth, even though that is preferable for more thourough care.
When I use a bow to play guitar and base it is a nice little gadget to have by your side when switching playing styles, since rosin makes your string sticky and hard to pick.
It removes the rosin (I played with cello rosin mostly) in just a matter of seconds and adds that soft oily and light feeling that you want in strings and that care products usually provide when strings become a bit tired.
However it didn't last long. Dried out in a matter of weeks and got really dirty since you can't really clean it without removing the cleaning agent.
And for more thourough care of your instrument you should of course use a proper care product like certain oils (I prefer lemon), which gives a better result.
Also it didn't give a very long lasting protection compared to other care products.
But if you as me switch between bow and fingerpicking, or maybe always eat burgers when playing, this might be for you :P hehe