Rather than secretly install a spy camera,which is possibly a criminal not talk to your wife and encourage her to bring her alleged lover home for you to meet him,and from thereon in,you will be the proverbial fly on the wall,,and she can then be totally at ease with the situation,

Trust me,,there is no finer feeling than being made to stay in the spare bedroom and listen your wife being made love to,,the squeals,,the moans,,the animal grunts as he unloads his ball bag deep into your wife..sit your wife down,,get yourselves a drink,,and embrace the situation.

good luck,