I have been told that recording a conversation in NY is ok if one party consents/is aware? but how does that apply to a sexual activity?
To confirm your first point, according to the Digital Media Law Project's website:
"New York's wiretapping law is a "one-party consent" law. New York makes it a crime to record to record or eavesdrop on an in-person or telephone conversation unless one party to the conversation consents. N.Y. Penal Law §§ 250.00, 250.05. [...] Thus, if you operate in New York, you may record a conversation or phone call if you are a party to the conversation or you get permission from one party to the conversation in advance."
As to your question regarding the application to sexual activity, according to another legal website:
"In a case of first impression that required a NY Appellate Court to look at decisions from Michigan and Indiana for guidance, the Third Department held that videotaping a consensual act without a partner’s knowledge violates New York’s laws against unlawful surveillance."
To sum up, if you are recording a conversation that you are engaged in, then, by all means, feel free to record it, but if the other party is using their mouth (or any other orafice) for something more intimate, then I would caution against any attempt to record said encounter.