Do you remove the row from the interface table once it's been processed?
As Manuel suggested, insert trigger is the best approach. But since you already have the code in your second app in place, then I think timer is the second best.
If you don't remove the row from the interface table, then a combination of trigger and timer might be a good idea. You create another table with the row inserted indicator. The trigger will increment the value by 1 everytime a new row is inserted, and your app decrements the value by 1 everytime a row has been processed. 0 mean no new row.