It depends on where the accounts are held, as there are a limited number of brokers that will deal with API interfaces. Most do not. If you are serious in pursuing this, open a 'Friends & Family' advisor account at Interactive Brokers. Your trades are made in a master account, and at the same time in sub accounts opened by others. Investor RT (www.linnsoft.com) will interface with IB via AutoTrader software. You can manually enter trades with chart buttons, and they will be sent to your IB master account, and to the sub accounts. The system works well, I have been using the IRT>AutoTrader>IB setup for about a year with no problems.
Current version of TWS have additional security measure that makes auto login impossible, so automation without human monitoring is not possible with current version of TWS.