Did you get an unwanted gift over the holidays? A new, Seattle startup, SwapViva, said last week that it has launched a new, mobile app which lets users list and sell products using their iPhone or iPad. The startup said it lets users post pictures and descriptions of products and services they'd like to sell, trade, or barter on the service. SwapViva was founded by Mihai and Alex Draghici. The two have a bold goal: to be a mobile competitor to Craiglist.