The mechanics behind it is simple. You create a note and assign it to your contact. When your contact calls, the note will pop up showing you the things that you need to know. In this case, you can save the embarrassment of forgetting the things you have promised. Install Bytnotes from the market (Appbrain link, costs $0.97) launch Bytnotes on your Android phone. Create a new note.
Once done, tap the back button to save the note. Tap on the icon beside the note. Choose from your contact list the friend that you want to assign the note to.
That’s it. Whenever your friend call, the note will appear.
In addition, you can set the reminder note to appear for both incoming and outgoing call. At least you know what you going to say before making that phone call to your friend.