NSInvocations
also have to have a target and a selector in addition to a method signature and arguments:
NSInvocation *invocation = [NSInvocation invocationWithMethodSignature:[self methodSignatureForSelector:@selector(timerTest:paramTwo:paramThree:)]];
NSString *a = @"a";
NSString *b = @"b";
NSString *c = @"c";
[invocation setArgument:&a atIndex:2]; //indices 0 and 1 are target and selector respectively, so params start with 2
[invocation setArgument:&b atIndex:3];
[invocation setArgument:&c atIndex:4];
[invocation setTarget:self];
[invocation setSelector:@selector(timerTest:paramTwo:paramThree:)];
[[NSRunLoop mainRunLoop] addTimer:[NSTimer timerWithTimeInterval:1 invocation:invocation repeats:NO] forMode:NSDefaultRunLoopMode];