If I were to make a neural network that predicts the value of e.g. Bitcoin tomorrow based on the chart of the last month, would that work? Of course, 100% accuracy cannot be reached, but a success rate over 50% on determining if I should buy or sell Bitcoin could be very profitable. Have there been any attempts to create such neural networks so far?
There are some academic works on that, but basically what you're asking for is a time-series estimation.
Here's a paper that tries to estimate Bitcoin price, for example: PAKDD: Forecasting Bitcoin Price with Graph Chainlets.