WARNING : This is not production ready!!!
It's pretty much a port of this plugin for jQuery: http://www.meiocodigo.com/projects/meiomask/
Just include the mask_input.js after your ember.js or ember.min.js.
{{view MI.MaskInput mask="(99) 9999-9999"}}
guilhermeaiolfi/emberjs-maskinput
An Ember.TextField that can have a mask for pre-defined inputs. e.g. (999) 9999-9999