Digital Sticky Notes

So you work in an office, and you take a bag lunch to work. You're wife packs your lunch, cause it's the 70's, or she's racked with guilt over her affair, I dunno. It's your birthday, and your coworkers have forgotten. Come lunchtime, you find a 'digital sticky note' resting on your potato salad. You press play and are treated to your wife and daughter singing happy birthday. Your boss overhears, remembers what his daughter was like at that age, long before she ran away with a gentile and stopped calling, and he generously gives you the rest of the day off, and heck why not a raise too. On the note, after the song, your wife reminds you to pick up milk and menthols on your way home. So you walk in the house, put away the milk, and go to tell your wife the good news, only to find her in bed with your sister, Angela. Recording a response to the birthday song, you tell your wife to expect a divorce, and stick the digital note on the front door as you leave, where a small light flashes to announce theres a response.

So the thing would be small, sticky, cheap, reusable. The sound quality doesn't have to be good, just a green light for a message, a red light for a response, sticky and magnetic on one side, and no bigger than a post it note, though thicker. I dont know about batteries or lcd screens or speaker sizes, just small, light and cheap enough almost to be disposable, so you can have a half dozen in a drawer by the phone, and another dozen scattered about in purses, cars, around the house.