Since going on meds I haven't felt that way but I used to get really paranoid thinking that people were watching me through electronic devices, laptop screen, phone tracking, etc. Also that people were standing outside shuttered windows trying to watch me sleep.
I used to take the battery out of my phone before I had an iPhone, and I cover my webcam but sometimes I feel like people are watching me through the screen (which I know in my head is impossible) or somehow watching my web activity or my computer screen.

I also once was convinced that my reflection was sentient and keeping me from passing into an alternate reality.