Riggle's wife, Tiffany, filed for divorce in October after 21 years of marriage, but Rob claims things got worse shortly after when $28,000 in emergency money went missing from his home office ...

Riggle claims Tiffany somehow had knowledge of private conversations he'd had in his home office either with or about his girlfriend and assistant, and she -- or other anonymous sources -- would text or email them referencing the private info.

And, get this -- Riggle claims one of the vids shows Tiffany standing on a ladder installing the spy camera, and another vid shows her sitting on the floor of his home office counting money ...