Help about surveillance

Hi, I'm looking for a hidden cam with power supply operating 24/7 reliable and with ftp and ddsn features.

I have a lot of doubts.

I tried some cameras in the past but for wireless ones sometimes the audio signal cuts off.

I've seen there are a lot of cameras on market but without brand and I don't know which I can trust on it.

Actually it would be enough for me only a microphone without video but it seems to me that there aren't devices with only audio signal.

Maybe it would be better only a wireless mic with a high gain and a good rate sound/noise but it must work well.

The device must be used for inside use.

Today I've just bought a cam but I don't know if it's a right purchase.

This cam (inside a charger) can be used with his software named Iminicam.

I don't know if you can set ftp, ddns or if you can use through some others app on phone.

Any suggestion is appreciate!!