If you have seen someone stand and repeat the same words over and over exactly as the first, most likely they are using a Runescape Auto Talker. The Runescape Auto Talker is a macro, also known as a bot, which takes control of your account and makes it do things, in this case type messages. Another example of a bot would be the Runescape auto miner. It takes control of your Runescape account and continuously clicks on the ore rock that you specify. Any sort of macro is illegal in Runescape, Jagex has built their own secret bots to "crawl" Runescape and look for suspicious activity. If the evidence is too great, they will act on it.
I do not in anyway support hacks, cheats, macros, bots, what ever you want to call it. I think that it is wrong, evil, and it makes the people who actually work for what they get feel worthless. You may think your not hurting anything by cheating, but what if everyone cheated and got all their skills level 99 and they maxed out their level? They would then sell the things that they acquired cheating, which would make the Runescape economy drop terribly. Then everything would become practically worthless, and people would own quite a few pairs of dragon armor, and it would not matter because there would be no challenges, then the Runescape population would die, so Jagex wouldn't get any income, and Runescape - runescape-blog.com would be forced to shut down. So think about that.
So now, let's look at what the Runescape Auto Talker does exactly. The Runescape Auto Talker is a program that will type the same message at a rate such as three seconds. So if we were to give it the words "Hey! Check out this article your reading about the Runescape Auto Talker!" and set it for every 10 seconds, anyone in chat range would get that message every 10 seconds. People often use this for advertising their items in the Grand Exchange, or to advertise a website.
Some auto talkers have built in special effects such as glow, scroll, wave, and flash. According to how it has been scripted, they can do anything that you could sitting there typing it yourself. However, if you were to have it at three seconds with the special effects, no doubt your threat level greatly increases - A perfect sentence with the same effects. Very suspicious, don't you think?
If you are seriously still interested in a Runescape Auto Talker, then a simple Google search will find a one. Beware, however, because many of these so-called Runescape Auto Talkers are really just keyloggers. A keylogger is a form of virus that tracks any keys that the person types. This way they can get not only your Runescape account, but also other personal information like your credit card information. They might also contain other viruses. People have designed some viruses to go into the computer's logged files and steal any information. Its almost like a more advanced keylogger, but instead of logging keys that are being typed, it goes in and steals keys that have already been typed.
If you are still going to get a Runescape Auto Talker, I suppose I cannot stop you, but I really do not see a point in it. The same time you spend sitting there with the Runescape Auto Talker on; you could be sitting and typing it. No hack, cheat, glitch, bot, macro, or any other cheating device is worth it. You turn one on to test it, you come back, and your account has been banned. The consequences are always worse than the gains.