http://jsfiddle.net/dhze/2mp65dkq/

murk.js

var murk = (function(w, d, pub, dev) {

  // state reference, mostly for 
  // dev/internal use and context
  var state = {
    model: {},
    dom: null,
    elems: {}
  };

  // only way to interact with our 
  // model, this way we can use this
  // loosely as an event emitter
  function setModel(obj, str, merge) {
    // we'll always set merge to true,
    // this way you're not overwriting
    // the model unless you intend to
    merge = (typeof merge == 'undefined' ? true : false);
    if (typeof str != 'undefined' && typeof obj == 'string') {
      state.model[obj] = str;
      // if we've set this elem before we'll
      // pass that reference if possible to
      // improve performance
      if (state.elems.hasOwnProperty(obj)) {
        return collectElems(state.elems[obj]);
      }
    } else {
      if (Object.keys(state.model).length || merge) {
        extend.call(state.model, obj);
      } else {
        state.model = obj;
      }
    }
    return collectElems();
  }

  // gets the model, yeye
  function getModel(key) {
    if (typeof key != 'undefined') {
      if (state.model.hasOwnProperty(key)) {
        return state.model[key];
      }
      return null;
    }
    return state.model;
  }

  // collects elems, allows you to
  // pass context so you can stay
  // super snappy
  function collectElems(ctx) {
    if (typeof ctx != 'undefined') {
      bindElem(ctx);
    } else {
      if (!state.dom) state.dom = d.getElementsByTagName('*');
      Array.prototype.map.call(state.dom, bindElem);
    }
  }

  // binds elem from model, simple things
  function bindElem(elem) {
    var attrs, key, count;
    attrs = attr(elem);
    key = attrs('data-murk');
    if (key) {
      if (state.model.hasOwnProperty(key)) {
        // we only want to modify elems that 
        // have changed their values
        if (decodeURIComponent(attrs('data-murk-val')) != state.model[key]) {
          if (!state.elems.hasOwnProperty(key)) state.elems[key] = elem;
          count = attrs('data-murk-count');
          // encode and set a reference of our 
          // newly bound value
          attrs('data-murk-val', encodeURIComponent(state.model[key]));
          // keep visual refence we're bound
          // to this elem
          attrs('data-murk-bound', true);
          // we want to keep track of how many
          // times we're interacting with this
          attrs('data-murk-count', (count ? parseInt(count,0)+1 : 1));
          // finally, set innerText to our value
          elem.innerText = state.model[key];
        }
      } else {
        attrs('data-murk-bound', false);
      }
    }
    return true;
  }
  
  // just a wrapper for elem.[set/get]Attribute()
  function attr(elem) {
    if (typeof elem != 'undefined') {
      return function(key, val) {
        if(typeof val == 'undefined') {
          return this.getAttribute(key);
        } else {
          return this.setAttribute(key, val);
        }
      }.bind(elem);
    } else {
      return null;
    }
  }

  // simple extend fn
  function extend(obj) {
    if (typeof this == 'object') {
      for (var key in obj) {
        if (obj.hasOwnProperty(key)) {
          this[key] = obj[key];
        }
      }
    }
  }

  pub.set = setModel;
  if (dev) pub.state = state;
  return pub;

})(window,document,{},true);