Well, don't worry, I spent all £1.49 of my money to try it for you
It isn't a scam, it does work - sort of. The output isn't high enough to get the full range of modulation, and this is at full "Amount" plus maximum headphone volume. The interface is horrible - the buttons are very unresponsive, and it only seems possible to get complex modulations.
So - is it worth a whole $2? Well, you're not getting anything like the kind of quality of app we have come to expect for even this tiny amount of money, but then I would struggle to buy even a single bottle of beer for this, and when you consider his potential market is pretty small, I don't begrudge having spent it.