I gather that Mist will automatically look for Geth on a local machine via IPC to save it maintaining its own blockchain. Is it possible to tell it to look for an instance of Geth on another machine via HTTP RPC?
This feature is available since version
You will need to start the node with RPC enabled:
Connect Mist via:
Mist --rpc http://localhost:8545
Please mind the security implications:
This is less secure than using local IPC - your passwords will be sent over the wire as plaintext. Only do this if you have secured your HTTP connection or you know what you are doing.
I disagree above with Péter Szilágyi and others. While yes it is not super secure to connect over rpc but it makes life much easier and gives a better architecture in terms of management and custom collaborative development on a private network. Besides mist as wallet/browser should truly do what it supposed to and rely on giant memory sucking space consuming geth process. Thats why services like BaaS getting popular and people shold be able to do connect to daap from their ipad/table and do some client side development.