Ariana Grande wore some very stylish silver in-ear monitors when she performed on Saturday Night Live - Sep 27th, 2014. They are called Ultimate Ears UE 18 Pro in-ear monitors.
Hers were "blinged out" with a silver jewel coating and immediately caught my eye when she started her performance.
One thing that is a bit out-of-the-ordinary about them is that they have very visible wires running from the ear phones behind her ears and down behind her shoulders, contrasting nicely with her black hair and almost acting as a fashion accessories in themselves. Plus, the shiny sliver jewel coating is not in the "standard" model either:). Typically, musicians want these monitors to be as low-profile as possible.
But even though there is a visible cable, most in-ear monitors (IEMs) are wireless. Those cables connect to a body pack that receives the audio wirelessly from the monitor/PA system. Of course that makes sense. It would be pretty hard to be on stage with 20 feet of tiny wires criss-crossing the floor!
Musicians wear in-ear monitors to hear themselves - and the rest of the band - better while on stage. The usual method for monitoring is to have monitor speakers - typically "floor wedges" - on the front of the stage facing back toward you.
If you don't have these, then it is VERY difficult to hear what you're singing/playing. And singers will often sing off-key or hit several bad notes when this is the case. Over the many years that I've watched SNL, I've noticed that some VERY good singers hit a lot of painfully bad notes while singing on the SNL stage.
And I've suspected that the stage monitoring situation there must be pretty bad for this to be true. So if I were going to sing on SNL, I would absolutely want to use in-ear monitors to give myself the best chance of hitting all my notes.
By the way, I should mention the difference between in-ear monitors and just earphones/headphones that you wear to listen to your portable music device. As I mentioned earlier, IEMs are part of a wireless system made specifically for singers and other stage performers to be able to hear themselves through the PA system so they know how the audience is hearing them.
When you're behind the PA speakers which are facing the audience, as performers have to be (otherwise you get terrible feedback when the speaker sound gets into the microphones), it's really hard to hear what's going on. All you get is whatever echo that bounces back off the walls from the rest of the venue.
That is why IEM earphones are usually so much more expensive than your typical ear buds for listening to your iPod/iPhone (or whatever). They have to do more than just play music back. They have to isolate, and they have to pay more attention to accurate sound rather than nice sound.
Consumer headphones and speakers want to make the music sound good. But reference monitors (which is what IEMs are) need to reproduce what is ACTUALLY happening, regardless of whether it sounds good or not. The good news is that IEM earphones can do both! In fact the excellent fit and isolation provided by the custom IEMs make them great for listening to your portable music device when they aren't being used on stage.
The UE 18 Pro in-ear monitors are not cheap ($1,350). Even so, PC magazine says "believe it or not, this earphone pair is well worth its outlandish price."
There are lots of other options out there (see below). But hey, if you have the money for them, why not? Based on reviews by several sites (PC Magazine review, Hi-Fi.org's review), these things do an incredibly good job.
PC Mag says "Unparalleled in-ear audio performance that even the snootiest audiophile will appreciate." There are six drivers in each ear to give detail to the entire frequency range. They go on to say "in-ear sound quality may have reached its apex: the outrageously priced Ultimate Ears UE 18 Pro earphones are a sonic masterpiece."
The UE 18 Pros are custom IEMs, which means they make them to fit perfectly into your own ears. In order to do this, you must provide them with a mold of your ear - yes, inside and out. Then they make them to fit.
Lots of IEM companies make custom ear phones like this. It requires you to go to an audiologist to create the molds for you. The UE site provides a list of recommended audiologists based on your geographical location. But any qualified audiologist familiar with how to make "open mouth impressions, full shell with CIC canal" will work.
More affordable in-ear monitors: