Virtual MIDI Piano Keyboard is a MIDI event generator and receiver. It doesn't produce any sound by itself, but can be used to drive a MIDI synthesizer (either hardware or software, internal or external). You can use the computer's keyboard or mouse to play MIDI notes. You can use the Virtual MIDI Piano Keyboard to display the played MIDI notes from another instrument or MIDI file player.
If you have a pre-determined quota from your operator of how much packet data you can use in a month, it's a pain to first find the Logs application, open the packet data counter, then try and work out how much data you have left from the amount used so far. Data Quota shows two simple bars: one showing how much of the data for this month you have used, and one showing how much of the month has elapsed. This lets you tell at a glance if you've been using data up too quickly or slowly, so you can be more (or less) frugal.