In a science fiction game, remote sensing equipment can sometimes be abstracted merely as "sensors" that seem to magically detect whatever needs to be detected at any given time. This is a perfectly fine way to approach the question in a game or other fictional setting, as evidenced by Star Trek.

On the other hand, you can break remote sensing gear down into a plethora of subcategories and differing sensory modalities. What is detectable by one sensor may not be detectable by another. In one sense*, even Dungeons & Dragons gets in on this, with its use of infravision and ultravision. With high tech gear, you can really go to town. You have the whole electromagnetic spectrum at your disposal, as well as vibrational waves including sound and seismic activity, and particle streams, plus any exotic science fantasy stuff you care to think of.

An alternative approach is to ignore the medium and build sensors that detect certain stuff, burying the technical details. You can have motion detectors, weapon system trackers, emotion sensors, or even precognitive sensors like in Minority Report.

The advantage of splitting your game world sensors up into numerous categories is that people might not have the right sensor at the right time...

* Pun definitely intended.

Transcript

GM: Luke, make a Spot roll.
Luke: 12.
GM: You see what looks like a meteor plummet to the ice, a couple of kilometres away.
[SFX]: paff!
Luke: Echo Three to Echo Seven. Han, do you read me?
Han: {over comlink} Loud and clear, kid. What's up?
Luke: I just saw a suspicious meteor. I'm gonna check it out. If I don't report back every 15 minutes, execute Protocol Omega.
R2-D2: Oooh. Nice protocol name.
Luke: I scan for any electromagnetic activity, radiation, unusual radio signals, neutrinos, gravity waves, or tachyons.
GM: Is that all?
Luke: Wait, also the Black Alpha subliminal sub-noise signal layers. Yup. That should do it.
[SFX]: RAAARGH!!!
{Wampa whacks him}
[SFX]: Smakk!