The cellphone/app seems like a weak link for such a safety critical system. Is there no other way to control the blinkers?
Above 20-30 mph (32-48 km/h) it gets easier, because the bike balances on its own and you don't need to hold the handlebars at all (you should though, for emergency braking and saving yourself from potholes etc.).
Keep in mind that most motorcyclist don't support the bike with their feet unless they're standing still - it's a good practice to keep your feet on the pegs as much as you can. It's way better to tip over than to lose your foot to the chain.
TLDR: I'd pick using hand signals on a bicycle over using them on a motorcycle every time.
I had an intermittent short in the indicator switch on a motorcycle. One day it suddenly started indicating left at an intersection when I was going straight. A car in the opposite direction was turning (their) left and almost hit me. According to the other driver my bike started indicating (my) left as I neared the intersection so it looked entirely intentional.
Fortunately we both had left ourselves safety margins and had eye contact so we didn't crash. But add youth, testosterone and aggressive driving and that could easily have been a really dangerous misunderstanding.