From all the Android apps I've tried, I'd suggest Clockwork Tomato.
It it's essentially a timer (offers a ton of settings, though)
has a beautiful UI, you can also use the widget it offers for quicker launch,
and can display history for all completed pomodoros, in columns for days, aligned by hour.
It also has these two great options:
- to "include unfinished pomodoros" in the log (eg. if you start a
pomodoro and press skip/stop before 25min - but at least at 60% of
it's duration) it will be proportionally be added to the log of
- Also it has the "auto-continue" option: when a timer ends, to
automatically start the following timer.
Then, it's also Pomodoro.txt
It offers a to-do list which you can order and filter by priority.
Then you can start a task with the option for pomodoro length of 10,25 or 45 min
It also history of completed pomodoros
and can sync via Dropbox in order to backup the to-do list.
Last, there is "TimeWise: A Pomodoro Timer" (google it - I can't post a third link in the same post, yet)
it also offers a to-do list, where you can assign pomodoro to each,
and also can display history of completed pomodoros.
I hope that in the next update it will improve, because it still has some issues.
And, for windows, it's XorTime (google it).
It offers a paper-like interface with a to-do list, an unplanned list, and an activity inventory
-all exactly as Pomodoro Technique instructs-
you can assign pomodoro to each,
also can dsplay history of completed pomodoros,
and can display statistics for all completed/bad pomodoros and interruptions.