Here is another thought. Could you use the sound the fingers make as they tap on the table to figure out what key was pressed? This might be hard on a normal ta

Here is another thought. Could you use the sound the fingers make as they tap on the table to figure out what key was pressed? This might be hard on a normal table. So a workaround could be a simple keyboard hardware device that emits a different inaudible frequency for each key. Now if two people are using this device near each other that wouldn't work. Wait. What about just using a keyboard with bluetooth. The iPhone can pick that up. That should solve all the issues. I am sure someone could make some money on a device like this.