No. If you have filed the necessary FMLA certification and your request for intermittent FMLA has been approved, your employer cannot check up on you in this manner. If they reasonably suspect that you are abusing FMLA leave, they can ask you for recertification sooner than the Act allows (every 30 days) and even send you to a doctor of their choosing for a second medical opinion but the Act does not allow the employer to send security guards to your house to check up on you.