I have developed different trading bots both for Forex and cryptos, following different strategies based on technical indicators and other miscellaneous trading approaches (arbitrage, etc.).
As far as I can see, Nadex has no programmable trading platform (Ninja Trading, MT4, etc) and also has no API (SOAP, REST API, etc.) as many other sites have.
If you want to implement an automatic trading solution, one of the first steps is to carefully select the right broker with the right tools.
If you decide to develop an automatic tradind system in any other site, let me know..