I wore a king of hearts monitor last month. They scheduled me to wear it for 30 days, but I got to take it off early because they caught the problem.
Anyway, mine had two sticky electrode tabs to place on your chest. You could unhook it to take a bath or shower and connect it again after. It would record events on it's own and you could also hit the record button. I believe mine would record up to 10 events before you would have to call them in. When you call them in it kind of sounds like a fax going over the telephone. I believe that information went to a 3rd party and they sent them to the doctor the next day. The monitor is about the size of a deck of cards.
It's an event monitor worn for a few weeks. Some people have arrhythmias that don't occur every day so in order to record what's happening, a person may be asked to wear an event monitor, sometimes called the king of hearts. My mom is wearing one now but hers is called the iMonitor. Same idea, different style.
The idea is you wear this little ECG monitor day and night. If your heart acts up, you can press a record button and it will save the information/ECG to be transmitted later. They vary whether they will store 2 or 3 recordings before transmitting the data over the phone. If you have to wear one, they will explain all the details.