An ear prompting rig is two things. Something that plays your voice back to you, and something that gets it into your ear without anyone seeing it.
Everything else is a variation on the second half. Concealment is the constraint that shapes the whole category, because a system that is visible is not working.
Earpieces
Wired. A cable runs from the earpiece down inside your collar to whatever is playing the audio. Reliable, cheap, and the cable is the problem. Fine for narration where you are seated behind a desk, difficult where you move or wear anything close-fitting.
Wireless. Usually a small moulded piece, close in design to a hearing aid, driven by an induction loop worn under your shirt. Nothing visible if it fits properly. More expensive, needs charging or batteries, and needs to actually fit your ear — a piece that works loose halfway through a take is worse than a cable.
Fit is the thing people underestimate. An earpiece that is slightly wrong is uncomfortable for the first ten minutes and unbearable by the third hour of a trade show.
The loop
A wireless earpiece needs something to transmit to it, and that is usually an induction loop worn around the neck under clothing, connected to the audio source. It is an old technology and a robust one.
Two practical notes. Loops are affected by their surroundings, so somewhere with heavy electrical noise can degrade what you hear. And a loop is another thing to hide, which matters more with an open collar than with a suit.
The audio source
Your recorded script has to play from something. A dedicated recorder, or a phone.
Working actors are split on this and the reason is interesting. A digital file plays from the beginning, and if the copy changes you re-record the whole thing. A tape can be nudged, paused, or wound back a little mid-performance, and re-recorded from a point in the middle when only one section has changed. That is a real advantage on a set where pages are being revised, and it is why some people are still using analogue decks.
Phones are the obvious modern choice and they work. Some actors avoid them on jobs for a simple reason: a call, a notification, or a low-battery chime arriving in your ear mid-take.
Concealment
The system is only working if it is invisible, which means planning for the wardrobe you will actually be in. Where does the recorder sit. Does the loop show at the neckline. Is the earpiece the far ear from camera. Can you get to the controls without a visible reach.
None of this is difficult. All of it is easier decided beforehand than during a setup.
What none of it fixes
Buy any of this and you still have a recording that does not wait for you. The lag discipline in how to use an ear prompter is required whatever is in your ear, and it is the part that takes practice rather than money.
Which suggests an order. The skill is the thing being bought when a producer asks for ear prompter proficiency, and you can find out whether it suits you before spending anything: an adaptive guide track in a browser needs one earbud and nothing else, on iPhone, iPad, Mac or Windows, in Chrome, Edge or Safari — the guide track is not captured on Android, and voice mode needs the Web Speech API, which Firefox does not have. That is covered in practising without the hardware.
Then buy the rig, if the work calls for one. A concealed system on a client's set is a genuinely different thing from a browser and an earbud, and no amount of software substitutes for it.
Not the same as an IFB
The earpiece in a news anchor's ear looks identical and does the opposite job. Worth knowing which you are being asked for: see IFB versus ear prompter.