Nothing can ruin a nice day outside quicker than unwelcome mosquitoes. Keep them at bay with this USB powered, ultrasonic insect repeller from Uxsight. It generates a low buzz, inaudible to the human ear while the mosquitoes do not like it and stay away. It is completely safe for adults and kids, as well as for your pets. It has an effective range of 1.5 square meters. You can get one for $5.69.