Can a notarized letter hold up in court regarding an agreement between 2 people?

Question Details:

My wife and I are getting a divorce and doing it ourselves. She is receiving monthly payments and promised me half since she would not be getting them if it weren't for me. The payments are in her name and if she didn't want to pay there would be nothing I could do. She said she would send me a notarized letter stating she would pay me for X amount of months. Will this hold up in court if she moves or just decides not to hold up her end of the bargain ? I also have it on recording her stating this which is legal in ID because she used recordings on her ex-husband. Important Notice