Please advise

Hi to all, I’m new here. The reason I came here is that I was looking for a gsm device which I can use as audio security monitor.
What I want to do is have a device where I can put a simcard, when I call the number of that simcard it picks up without making any sounds, sothat I can hear what happens in the secure room. So I searched the internet and found a small device they call it simbug, there are 2 most known models, one is about 50$, other is about 100$ well I ordered both of them, the 1st cheap one is really big mess, you can call to it, you can hear only things next to it, like maximum 1meter(i opend it and discovered that they just put an old used gsp phone board inside and made some hand work soldering). The other one the expesiver one has better sound quality, but still does not take more than 3-4 meters radius. So I opened the second one,expensiver one. I saw there is a wavecom board inside. This device is 6 by 4 sentimeters. so I came on this website to see the wavecom, now I see wavecom sells this boards. I need to know which board is best for me, and I want to know with wich board and microfon and battery I can achieve the best voice quality the farest voice recive radius like maybe 10 meters, longer battery time. I’m in security business, delivering alarms for ofices and shops. in some cases the clients want to listen to their office when they are absent. for this purpose I need this devices. The device which costs 100$ has 15-30 days standby time (the user manual says that) and it has about 5-10 hours listening time. I dont know if Wavecom delivers this devices ready to use, or I must buy the boards, microfons, batterys , software separatly and than somehow put it toghether ? Please advise.

forgive me if I sound stupid :slight_smile:.