a pet peeve of mine, usually in sci-fi but sometimes other genres, is what I call the Transmitter-Receiver Problem
Imagine you are trying to send someone a message and you want to send it by radio signals. The good news is that you have a radio transmitter. The bad news is the person you're sending it to doesn't have a receiver. Are they going to get your message?
Sci-fi doesn't usually make this mistake with radio (or other things that actually exist, like phones), but with more speculative or fictional technologies it does come up, especially teleporters
It's one thing if you are the teleporter, like Nightcrawler, but if your teleportation relies on using a machine then the Transmitter-Receiver Problem does apply. If your machine converts matter to energy and then transmits it to a desired location I would like to know what converts it back to matter because otherwise you just killed your entire landing party
Another example is telepaths, and that's actually one I'm usually willing to handwave but I still want to bring it up because Sense8 does a good job of avoiding the Transmitter-Receiver Problem with its telepaths: sensates can communicate telepathically but only with other sensates. And even then there's an additional requirement I'll come back to
Aside from satisfying nitpicky nerds like myself, keeping the Transmitter-Receiver Problem in mind also allows you to impose constraints on your characters, which can create more varied situations and by ruling out certain obvious/direct courses of action can give you and your characters an opportunity to show off how clever and creative you can be
And when I'm talking about constraints I don't just mean there having to be a receiver at the other end - even if there is one, it might not pick up the signal. To use another analogy - if you're trying to call someone and they do have a phone but you don't know their number, you probably won't be very successful (the radio version would be making sure you're using the same frequency)
And that's the other part of how Sense8 handles its telepaths that I said I was going to come back to - sensates can only communicate telepathically with other sensates but this does not mean they can communicate telepathically with all sensates. They have to either be part of the same cluster (short version - other sensates born on the same day as you, your telepath powers usually manifest at the same time and you basically always have a mindlink with them) or form a link by making eye contact
