A neat bot would be one which automatically buys and then resells things with a markup. It would figure out the usual price an item goes for on a website like Ebay, and purchase it if the price is set far enough below.
I have always wanted to try something like this with stocks or commodities. Make a bot watch the market, and buy and sell. I even got far enough to imagine some sort of genetic filtering, aka give the master bot 10k, then it distributes it to 10 bots, all which are slightly different, they spend it, the master takes any profit above 1k and invests it in another bot that is a combination of the best 2. Etc. That way y…
1) If you make something like 3 intra-day trades (buy and sell on the same day) in some defined period (a week?) the SEC will classify you as a "pattern day trader". To be allowed to do that, you need an account with something like $25k USD min.
2) There are a few items that people often forget in simplified models that will completely eat any theoretical profits: brokerage fees, taxes, and currency-exchange effects (e.g. if you're a Canadian trading US stocks).
3) After all that, you're competing with the big guys who have a deep knowledge of how trading works, and fast access to more information than you do. It's an insider's game.