Zulutrade was the first company to introduce a service that you can follow someones signals. Then, because it had great success, other companies followed. I find zulu more reliable than the rest, but still there are many things you need to be careful with when selecting providers, such as whether they trade from a live account, how much DD they have, average pips/trade, aver. trade time, etc. Its all there, you just need to make some research and use it on a demo account!