OpenWRT is a great embedded Linux platform for building router software. It runs in very constrained environments with no user interface (UI). It is also an interesting candidate for headless Android, since most routers do not have a UI besides the web type configuration engine.
Back in 2009, Felix Fietkau attempted to build Android on OpenWRT. The routers that were available to run OpenWRT at the time were even more limited than today's models. Both OpenWRT and Android have matured considerably since then.
Felix original efforts can be found here:
He has a borg.git repository that is mentioned in that blog post where he has picked up work on this again. It's an interesting exercise and I wish him the best of luck in making progress on that port. It would be really handy to see a working Android on an OpenWRT platform.