I agree with the same philosophy (or the very least have the ability to control the symmetry of the binding). I have been working on a binding library that allows you to have control over the binding (one-way, two-way) and which objects can be observed. It is simply a framework for defining hooks which provide APIs for defining channels (bindings) between various objects. There are hooks for jQuery, Zepto, Backbone, and plain objects: http://bruth.github.com/synapse/docs/

Disclaimer: I developed Synapse.