This looks like a free fun app that is available right now: Post-it® PopNotes – 3M Company. If you love Post Its and have an ipad or iphone you can now continue your love on these devices..
Create. Place. Share. The PopNotes App creates geo-triggered Post-it® Notes for the digital world. Create and place notes anywhere you want. Choose to leave a note just for yourself or share it with friends, family or everyone. You can even set a note to pop up at a specific time and location.