Hi John,

There is no such functionality out of the box currently, but I think it can be easily achieved with a custom  logic.
Here is my suggestion:
Create an instance of igDataSource bound to remote url. Configure the data source to use paging.
Call igDataSource.dataBind() on the data source in order to get the first page. Bind igGrid to that data (use igDataSource.dataView() to get the data from the data source.
Next you need an interface for the user to load more data to the grid. Let's have a button with caption "Load More Data…".
Use this button to call the data source igDataSource.nextPage() method. Calling the igDataSource.nextPage() method will request the next chunk of data. Get the data with the igDataSource.dataView() method and add it to the grid my using the igGrid.renderNewRow() method.
This approach will work for a simple grid scenario, without features. If you need more complex scenario, for example where local filtering and local sorting are used you need to use the data source of the igGrid (which you can get with this code: $("#grid1").data("igGrid").dataSource) and call its addRow() method. Then you need to rebind (call igGrid.dataBind()) the grid in order for reflect the change.

Hope this helps,
Martin Pavlov
Infragistics, Inc.