My guess, and it is only a guess since I am not the judge, is, that he better be ready to register as a sex offender because his crime falls under the definition of a sex crime. Voyeurism is a sex crime.
In the future we need to know what state the crime took place in, so that we can look up the pertinent laws to better advise you. Also, you did not state the charges that he pled guilty to. I guessed "voyeurism" because of your description of the crime. If he has pled to a lessor offense than that, it's anybody's guess what the judge will order.

