If you actively trade on the cryptocurrency exchanges and haven't heard of Cryptoping then you're probably missing out. They provide free alerts from most of the exchanges. Bittrex and Poloniex are just a couple of examples.
Cryptoping's alert services won't be free for long though. They currently have a live ICO and will be switching over to subscription based very soon. If you don't have any of their PING coins, you won't be able to use their service. They are actively developing and their [roadmap](https://cryptoping.tech/roadmap] looks very exciting.
For more information you can see their white paper.
Sources The Merkle.