onkeypress : onKey( 'enter', save ), etc

onkey.js

var onKey = (function(){
	var keymap = {
		'enter' : 13,
		'space' : 31,
		'tab'   : 9,
		'esc'   : 27,
		'left'  : 37,
		'up'    : 38,
		'right' : 39,
		'down'  : 40
	};
	
	return function bind( key, callback ){
		if( key in keymap ){
			key = keymap[ key ];
		}
	
		return function handler( e ){
			if( e && key === e.keyCode || key === String.fromCharCode( e.keyCode ) ){
				callback.call( this, e );
			}
			else {
				m.redraw.strategy( 'none' );
			}
		};
	};
}());

Usage

m('input', {
  onkeypress: onKey('enter', yourkeypresshandler) 
})