In terms of acquiring the step data, are you intending to use some kind of hardware to automatically do this, or would the user be inputting this data manually?
In terms of managing the data, there are two main aspects:-
1. Storing it. This could be achieved by creating a very simple database table containing two columns:- date, number_of_steps
2. Presenting it to the user. Can be done by presenting a ListView.
But it really depends what you mean by 'managing the data'.