Crypto auto-trading app or service?

For those that may have accumulated some level of crypto via mining for example, is there a way to make your hard earned crypto work even harder for itself?

I have been watching the cyclic wave of ETH going up and down and up and down, and it almost seems like you could casually sell high, wait for a dip, and then re-buy it, and repeat the process. Are any of the exchanges doing things like this where they may trade the one currency on highs and lows, or do even more automated things like watch other volatile altcoins to grow a portfolio somewhat automatically?

Is there an app out there that might be doing this already, even it is for a fee or a commission? I don't have time to watch the charts all day, but I could look at them sporadically, and I think I could make some money doing so, just buying on lows, and selling at peaks or at least near peaks. Can someone recommend something I might be missing?