Orbot should play nice w/ WhisperCore netfilter API
Note, we've begun development on this feature in the past, just creating a ticket now so it's trackable.
It would be super to have Orbot's transparent proxying capabilities on non-rooted devices. WhisperSystems has provided an API to do just this within their WhisperCore ROM.
SDK available here: http://www.whispersys.com/sdk-docs/reference/packages.html