You’d need the social skills to demonstrate technological improvements (say, a better axe) without causing everyone to freak out and call you a demon. You’d also have to keep your phones and charging devices secret until after you’ve recruited a few technophiles because otherwise someone is going to break them accidentally when they confiscate them for one reason or another.
Basically you need to recruit a few smart people who can be trusted and get them on your side. You might even want to funnel all your “inventions” through them to keep the heat off you, and this is assuming you end up in a culture that would even value technological advancement.