I made this trying to recreate iOS assistive touch. It's pretty basic, i have added snap to borders and show/hide animation. You can find an implementation in my repository "Tweak".

Draggable UIView

@interface FloatingView : UIView

-(void)dragged:(UIPanGestureRecognizer *)sender;
-(void)snapToLeft;
-(void)snapToRight;
-(void)snapToBottom;
-(void)snapToTop;
-(void)collapse;
-(void)show;

@end

@implementation FloatingView
-(instancetype)init{
	self = [super initWithFrame:CGRectMake(ScreenWidth,270,55,55)];
	return self;
	
  self.backgroundColor = [UIColor redColor];
	self.userInteractionEnabled = YES;
  
  //DRAG
  UIPanGestureRecognizer* panRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(dragged:)];
  [panRecognizer setMinimumNumberOfTouches:1];
  [panRecognizer setMaximumNumberOfTouches:1];
  [self addGestureRecognizer:panRecognizer];
  [panRecognizer release];
  
  /* // ------ UNUSED IN THIS FILE, CHECK IMPLEMENTATION IN REPOSITORY "TWEAK"
  //DOUBLE TAP 
  UITapGestureRecognizer* doubleTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(switchSocial:)];
  [doubleTapRecognizer setNumberOfTapsRequired:2];
  [self addGestureRecognizer:doubleTapRecognizer];
  [doubleTapRecognizer release];
  
  //SINGLE TAP
  UITapGestureRecognizer* singleTapRecognizer = [[UITapGestureRecognizer alloc] initWithTarget:self action:@selector(showSocialModel:)];
  [singleTapRecognizer setNumberOfTapsRequired:1];
  [self addGestureRecognizer:singleTapRecognizer];
  [singleTapRecognizer release];
  [singleTapRecognizer requireGestureRecognizerToFail:doubleTapRecognizer];
*/ // ------ UNUSED IN THIS FILE, CHECK IMPLEMENTATION IN REPOSITORY "TWEAK"
  return self;

}

-(void)dragged:(UIPanGestureRecognizer *)sender{

    if (sender.state == UIGestureRecognizerStateEnded){

        if(sender.view.center.y > [[UIScreen mainScreen] bounds].size.height-100){
            [self snapToBottom];
        }
        else if(sender.view.center.y < 100){
            [self snapToTop];
        }
        else{
        if(sender.view.center.x < [[UIScreen mainScreen] bounds].size.width/2){
            [self snapToLeft];
        }
        else if(sender.view.center.x >= [[UIScreen mainScreen] bounds].size.width/2){
            [self snapToRight]; 
        }
    }}
    if (sender.state == UIGestureRecognizerStateChanged){

    CGPoint translation = [sender translationInView:sender.view];
    sender.view.center = CGPointMake(sender.view.center.x + translation.x, sender.view.center.y + translation.y);
    [sender setTranslation:CGPointMake(0, 0) inView:sender.view];

    }

}

-(void)snapToLeft{
    [UIView animateWithDuration:0.3 delay:0.0 options: UIViewAnimationCurveEaseIn animations:^{
                     assistantView.frame = CGRectMake(5,assistantView.frame.origin.y,[assistantView bounds].size.width,[assistantView bounds].size.height);
                 } completion:^(BOOL finished){}];
}

-(void)snapToRight{
    [UIView animateWithDuration:0.3 delay:0.0 options: UIViewAnimationCurveEaseIn animations:^{
                     assistantView.frame = CGRectMake([[UIScreen mainScreen] bounds].size.width-[assistantView bounds].size.width-5,assistantView.frame.origin.y,[assistantView bounds].size.width,[assistantView bounds].size.height);
                 } completion:^(BOOL finished){}];
}

-(void)snapToBottom{
    [UIView animateWithDuration:0.3 delay:0.0 options: UIViewAnimationCurveEaseIn animations:^{
                     assistantView.frame = CGRectMake(assistantView.frame.origin.x,[[UIScreen mainScreen] bounds].size.height-[assistantView bounds].size.height-5,[assistantView bounds].size.width,[assistantView bounds].size.height);
                 } completion:^(BOOL finished){}];
}

-(void)snapToTop{
    [UIView animateWithDuration:0.3 delay:0.0 options: UIViewAnimationCurveEaseIn animations:^{
                     assistantView.frame = CGRectMake(assistantView.frame.origin.x,5,[assistantView bounds].size.width,[assistantView bounds].size.height);
                 } completion:^(BOOL finished){}];
}

-(void)collapse{
    [UIView animateWithDuration:0.2 delay:0 options:UIViewAnimationOptionCurveEaseIn animations:^{
        self.transform = CGAffineTransformMakeScale(0.01, 0.01);
    } completion:^(BOOL finished){self.hidden = YES;}];
}

-(void)show{

    self.transform = CGAffineTransformMakeScale(0.01, 0.01);
    self.hidden = NO;
    [UIView animateWithDuration:0.2 delay:0 options:UIViewAnimationOptionCurveEaseOut animations:^{
        self.transform = CGAffineTransformIdentity;
    } completion:^(BOOL finished){}];
}


@end