You could get a refractometer. http://morebeer.com/view_product/18739 Deal of the day today at $49. See homepage. No wort temp concerns either. Only takes a drop.
Refractometers can be had for ~$35 on ebay. When I first got mine I would take both hydrometer and refractometer readings but eventually found that the beer smith refractometer tool is accurate enough to stop using the hydrometer completely.