The one they run on sale at Midway or Harbor Freight has never failed me. Usually it blinks the display for a long time when the battery is low while it still works. I think you can buy a card of 24 batteries for it for $4 at HF too.
PRESS MONITOR - The ULTIMATE Press Accessory
Can Prevent Squib or Double Charge . Press Action Monitoring . Loaded Round Counter . Low Powder Alarm . Press Light . Rounds Per Hour