[bes]

хром

<input value="select some text">
<div style="position: absolute; display: none; background: lightgrey; color: green"</div>

<script>

	document.body.children[0].onmousedown = function () {
		this.onmousemove = function (e) {
			e = e || event; 
			this.nextElementSibling.innerHTML = document.getSelection();
			var hint = this.nextElementSibling;
			hint.style.display = 'block';
			hint.style.left = e.clientX + 'px';
			hint.style.top = e.clientY + 10 + 'px';
		}
		this.onmouseout = function () {
			this.nextElementSibling.style.display = 'none';
			this.onmouseout = null;
			this.onmousemove = null;
		}
		this.onmouseup = function () {
			this.nextElementSibling.style.display = 'none';
			this.onmouseup = null;
			this.onmousemove = null;

		}
	}

</script>