you can pick up an acu-temp hydra/thermometer from wal-mart or home depot for about $15
ideally you would get 2 digital thermometers with probes mouth them both under the substrate one on hot side on the glass over the UTH one on the cold side and get a separate digital hydrometer and mount it center tank about an inch above the substrate. the acu-temp thermometers have a hydrometer on it too but measuring humidity from under the substrate will be inaccurate.
anything with a dial or needle or those stick on temperature gradient stickers are all highly inaccurate and should barely b trusted with ambiant air temperature.