It's dangerous business calling any tech innovation idiotic these days. The next thing you know, the company's worth $50 billion. But it is hard to imagine many (hearing) people beyond the odd dorm-room prankster wanting to own Olly, a USB plug-in that allows you to associate smells with your computer's pings. (Then again, this may just be a marketing issue. The creators seem to have made the thing just for the fun of it, and no one yet seems to have recognized its potential for the deaf or hard of hearing). 

Available from London's Mint Digital Foundry, Olly is a white box into which you place the essence of whatever scent you want it to emit when you get emails or tweets or calendar reminders. By stacking several Ollys, you can assign a separate fragrance to each service.  One imagines that future Ollys will enable you to assign scent-labels to, say, your boss, your guru, and your ex-girlfriend who you're still kind of friends with.