Dev:SBSyncController

From The Apple Wiki

Kill all applications in switcher

1. First kill all the applications

[(SBSyncController *)[NSClassFromString(@"SBSyncController") sharedInstance] _killApplications];

2. Then remove the applications from the switcher

iOS 7

[[[NSClassFromString(@"SBAppSwitcherModel") sharedInstance] valueForKey:@"_recentDisplayIdentifiers"] removeAllObjects];

iOS 8

[[[NSClassFromString(@"SBAppSwitcherModel") sharedInstance] valueForKey:@"_recentDisplayLayouts"] removeAllObjects];