In Strategy Mobile 9.2.1 and newer versions, it is possible to use selector to highlight the selection on a chart. The following steps show an example to achieve this with Strategy Tutorial project:
1. In Strategy Web, create a report R1 with the attribute Year and the metric Cost.
2. Ceate Report Services document D1 based on R1.
3. In D1, insert R1 as a grid, insert an element selector for Year, and a blank panel stack, as shown below:

4. Right click on Year attribute in grid, choose using as selector to target the blank panel stack, as shown below:

5. Set element selector's target to the blank panel stack, as shown below:

(Note: The grid should not be selected as target here).
6. Right click the blank panel stack, in Properties and Formatting, uncheck "Visible" option, as shown below:

7. Turn the grid to a pie chart.
8. Run the Report Services document on iPad. Change selector answer to 2008, the pie for 2008 is highlighted, as shown below:

NOTE: This workaround is currently only possible in Strategy Mobile. In Strategy Web, an existing enhancement has been raised. Contact Strategy Technical Support for an update of this issue.