Sounds like you'd want this, but for it to truly work, you could also end up suffering. For example:
> A GPS spoofer that will occasionally tell my phone that I am visiting places I don't.
Sure, but the next time you want to see your Google Maps history, you'll question your own sanity.
> some kind of speech synthesizer which mimics my voice and sends engineered requests to Alexa while I'm not around.
Sure, but then you're liable for everything your spoofer says if it truly isn't distinguishable from your own voice. If it is distinguishable, then it defeats the purpose of hiding your true behavior in the first place.