I've just done some research recently . As far as know , 3-rd party charting or backtesting software like amibrokers and multicharts support auto-trading with IB, through IB TWS. it should be same if I use IBPy or IBridgetPy . IB TWS should be turned on always. As for I know , quantopian and collective2 are the tools that does not require TWS. I have not tried yet , but it looks like that. I wonder if there are any tools that do that. Thanks for any comments.
IB Gateway is your best alternative. It uses way less RAM and CPU than the TWS. If you use Gateway make sure you change the API port. The default API port for TWS and Gateway are different.