How to get the focused cell value at the time focussing on the cell by using the keyboard arrow keys
You can either get the focused cell by using
var focusedCell = gridOptions.api.getFocusedCell();
or use the onCellFocused event.
Both give you the following properties:
Use the row-index to retrieve the row-node:
var row = gridOptions.api.getDisplayedRowAtIndex(rowIndex);
After that you can use those properties to retrieve the raw value of the cell:
var cellValue = gridOptions.api.getValue(colKey, row.node)