Whistle announced a new GPS device to make sure you never lose your pet. The new product, dubbed WhistleGPS, uses both GPS and sub-GHz cellular technology to add on-demand location monitoring to Whistle's flagship activity tracking gadget that syncs with iOS or Android devices. It's a logical addition, as Whistle's core product seems best suited for pet owners who aren't always physically with their dogs. The gadget, which is on presale now for $49, will retail for $129 with a $5 per month GPS service fee.