* A timer. Touch the clock for a menu - general settings, timer settings - with
  the app's version and addresses at the foot of it.
* Timer settings: presets of named intervals, each with its own colour, the
  colour it moves to as it runs, a message spoken when it begins, and a warning
  so many seconds before it ends.
* On the clock: a bar down the left in landscape, across the top in portrait,
  filling as the preset runs, with the time so far, the time left and the whole
  length beside it, and hourglass, stop, pause and play at the end.
* It counts you in and out - three beeps and a higher one landing exactly on
  each ending, a melody when the whole preset finishes - or vibrates instead, or
  says nothing. The screen flashes at every ending either way.
* Switched off, the clock is exactly what it was.
