Clever Dave Evans, 41, fitted his ultra-light GPS gadget to Yollo’s collar when the tabby mysteriously put on weight after regularly sneaking out.
Dave uploaded the gizmo’s information when the cat returned and plotted his every move on Google Maps — discovering that the puss was chasing chickens.
The dad of two said: “My cat was getting fat even though I was feeding him less and I needed to know what was going on.
“Now I know he travels a couple of miles a day, where he goes at night and who’s feeding him. I know he also enjoys chasing chickens at 6am every morning and can see his favourite hang-outs.”
Dave, of Marlborough, Wilts — who has a background in satnav marketing — has called his 15g waterproof catnav gadget “G-Paws”.
He is now putting others on sale at £50 each — to be used on both cats and dogs.
The inventor is also developing a social networking site for pet owners to accompany G-Paws, which will be available in the summer.
He added: “It will enable users to see where their pets have been as well as share photos, videos and other information.
“For too long we have been kept in the dark about the secret lives of our pets. At last we will know what they get up to.”