(let us be pinged?)
Depends on whether we want to make the base verb pingo, pingere or pingo, pingare. I see that pingare has made it into Italian as a neologism for computer pinging, so perhaps there’s a Latin verb pingare (my dictionary is not at hand), alongside pingere (to paint, draw).
So, pingemus would be “let us ping” (subjunctive active) and all you need to do is make it subjunctive passive: pingemur = “let us be pinged.” At least I think that’s right.
Or perhaps you wanted an imperative: “pinga” — (you) ping (someone)??