Research is even more important in the collectible car market because buyers often hitch their hearts -- and their wallets -- to the bumpers of pricey cars for which they often overpay. For that reason, the Chubb Group of Insurance Companies is offering the free "Classic Car Guide" app for iPads and iPhones. The app, powered by "Keith Martin's Sports Car Market's" database of more than 100,000 auction entries, provides up-to-date and accurate sales information for domestic and foreign collectible cars. Users can search the collector car transaction data by vehicle identification number (VIN), make, model and year …