Science can't explain magic - but that doesn't mean science can't detect it. Modern fantasy is full of cool gizmos that can identify sources of mystical power... and even track them down. Here's our list.
Everything in Ghostbusters. This is the movie that perfected the magic-handling gadgets motif, from the "ghost sniffer" to the ghost detector, to the ecto-goggles, to the giga-meter... pretty much any kind of gizmo you might need to figure out the location of an evil spirit, Egon whips up at one point or another. And they all look awesome, as a bonus.
The BTRS detector in The Middleman. Our studly science hero uses a BTRS (Beyond The Realm Of Science) detector to scan for things that are, well... beyond the realm of science. As Wendy says: "Handy."
The Dragon Detector from Questors by Joan Lennon. In Lennon's fantasy novel, our hero Bryn has a gadget called a "dragon detector" which gives off an awful noise when the dragon Dagrod comes near it. As Bryn explains to Dagrod, "Apparently you give off a sort of radiation, and if I wanted to know if you were around, or coming closer, or something, this would tell me..."
The EMF detector, from Supernatural. Turns out that ghosts and other nasties give off electromagnetic fields, which you can detect with a handy gizmo. So in almost every episode of Supernatural, Dean Winchester whips out his flashing whizbang at some point. Which is very DIY, as Sam discovers in "Phantom Traveler":
Sam: What is that?
Dean: It's an EMF meter. It reads electromagnetic frequencies.
Sam: Yeah, I know what an EMF Meter is, but why does that one look like a busted up walkman?
Dean: Cause that's what I made it out of. It's homemade.
Sam: Yeah, I can see that.
People actually use these things in real life, and the guys on Ghost Hunters also use a similar rig to look for ghost signatures. And I love these gizmos.
Fairy detector in The Fairly Odd Parents. Mr. Crocker, the only adult who believes fairies exist, builds a fairy detector. And before his memories of his own godparents were taken away, he scrawled "Fairy Godparents Exist" on the back of a fairy detector.
Tricorder from Star Trek. The crew of the Enterprise frequently visits worlds where magic, of some sort, appears to work, including in the episode "Catspaw" and the animated episode "The Magicks Of Megas-Tu." Frequently, even if these magical mind-energies are not susceptible to human technology, they can be tracked to their source using Spock's tricorder, and some good old human ingenuity.
The "Ectoplex" Paranormal Energy Detector, from Sabrina The Teenage Witch. It zeroes in on paranormal energy fields and supernatural phenomena, as you can see in this clip (around the four-minute mark):
Dragon Radar from Dragonball. It's used to find the mystical dragon balls which summon the wish-granting dragon Shenron when you gather all seven of them together.
The Spook Detector in Caballistics, Inc., a comic that's been running in British anthology series 2000 A.D. since 2002. One of the paranormal investigators in the newly privatized Department Q is Hannah Chapter, who comes equipped with her own "spook detector."
Vampire Detector in Tales From The Crypt, "Fare Tonight." Two young girls, Mildred and Camille, decide to become amateur vampire hunters, and so they build their own homemade "vampire detector" gun, in this 1993 episode. And here's a picture of a cool Steampunk vampire detector that someone built as part of a costume.
The Emergency Detector in Ultraman. The Science Patrol all wear special tie-pins which blink and react when a monster gets too close. This is their "emergency detector."
So what did we miss?
Additional reporting by Alasdair Wilkins.