Former Disney Channel star Demi Lovato has been enjoying the wild success of her latest summer anthem "Cool For The Summer" and in the midst of her first-day performance at Las Vegas' iHeartRadio Festival, the singer stormed the stage in a bodysuit to perform renditions of "Really Don't Care," "Heart Attack" and her latest single. Making the show a bit more unique, Lovato executed a duet with Third Eye Blind front man Stephan Jenkins on the band's 90s smash hit, "Jumper."