Perhaps suitable for emergencies, but there are far better commercial products that can turn your mobile -- especially your tablet -- into not only a signal generator, but a logic analyzer, oscilloscope, spectrum analyzer, etc.
I remember at a trade show in the 90s, an engineer talked about a colleague who held up a PDA and asked him what it was. The guy replied that it was a Palm Pilot. His colleague said,"No, it's a 286 computer." That smart phone in your hand? It's got more processing capabilityand more memory than the early Cray computers. Think about it – a supercomputer in your hand. We live in amazing times.