I use Quantopian to paper trade a simple algorithm I developed and tweaked over the years, and then check daily and manually execute the trades with with my own broker (Questrade in Canada, which isn't supported by Quantopian's live trading platform).

Quantopian is literally the single most disruptive product in personal finance that I know of: https://www.quantopian.com/

(Not affiliated in any way. Just a really happy user.)