To the posters saying that it's hysteria to suggest that there are already spy devices in place in the OP's home, no it isn't. And even if this is the first attempt at spying on the OP, the fact here is that now that the OP knows that her h is planning to install a camera somewhere in the house to check up on her, and that knowledge alone is going to create a feeling of uncertainty and paranoia as to when and where she is being watched.
I wouldn't necessarily be worried that she hasn't come back. Chances are that she knows her h likely has keyloggers and/or remote access on her laptop so he can either watch her posts as they unfold or can download them at a later time to read.
Don't play games though. He is either spying because he's a creepy control freak, or because he believes he has good reason to spy. Let's not forget that on MN posters regularly advocate installing keyloggers/cameras etc to posters who suspect their husbands of cheating. If the OP's dh has got it into his head that the OP is having an affair he may have done exactly that. Either way, even on here, spying on someone in any context is out of order and if you've reached the point in your marriage of installing keyloggers and/or cameras in your house to catch someone out then the marriage is over because the trust has clearly gone. And when the spied-on person finds out then the trust will be gone on both sides.
So, no games. No dancing in front of the camera, no private detectives, but do let him know that you know. Change all your passwords from a computer he doesn't have access to. If the camera arrives open the parcel and just ask him outright what the hell it's for and why he lied to you.
These men think that they're impervious and untouchable. The reality is that they don't actually think that they'll be found out, so when they are it throws them completely.
My H spied on me I think now for the duration of our marriage. When we entered into the realms of having social media I think he found it much easier, and I trusted him so never changed my passwords so he found it easy to just log into every single one of my accounts and see what I was doing on them, not much as it turned out but he became obsessed. The more he didn't find, the deeper he had to go, until he had installed apps to follow me if I went out, had bugging devices in the house, remote access on the computers and the list goes on. But he got cocky. He would make reference to private conversations I'd had with people that he could only have known about by accessing password protected messaging on fb for instance. He would say something and then gaslight me into thinking that I'd told him what had been said, except he did it too many times and I became suspicious.
So one day when I knew he was at a work meeting I changed every single password by using a mobile phone he didn't have access to. It took me half an hour. Then I started using the computer for boring stuff only. No social media, no personal conversations, no discussions of any nature that would be grounds for checking with a keylogger.
And it drove him mad because I didn't say anything. Not a word. I just pretended as if nothing had happened, but after a week of not being able to access anything I said or did he came clean and admitted it, because he'd tried to access something and been unable, and then realised that all my passwords had changed seemingly all at the same time, so he knew that I had to have known.
At the time he blamed insecurities. But after that I never trusted him again and I was right not to. After that he bugged the house, had me followed, and when I found out I pointed out that even if we'd gone to counselling and tried to save the marriage, the thought of constantly being watched and listened to would mean that I would never again feel safe in my own home. Even after we got divorced I found out that he had several naked pictures of me taken by remote cameras when I was unaware which he'd kept over the years.
There is no valid reason for ordering a remote camera and not telling your partner about it. I would be getting my ducks in a row and making plans to leave. Because even if this is the first time, there is no way of knowing that, and no way of ever knowing which parts of your life are private and when you are being watched.