I have a directive that is instantiated like this:
Inside the directive, the datepic
Depending on how complicated your passthrough is, you can just use the = scope to do a bidirectional bind between a local name and ngModel, like in this fiddle:
http://jsfiddle.net/mThrT/22/
I had a hell of a time setting up the fiddle for some reason (first time trying with angular) but here's the money shot:
template: ''
+ ''
+ ''
+ '',
scope: {
bar: '=ngModel'
},