Possible to Flag failed and successful imported record

Hi Guys
We are trying create a scheduled record import via SOAP (Web Services) from an external system and have couple of questions

Qurtsions
1.     Is there a flag or field we can use when importing data to know which records we have imported already and which haven’t? If our services run on a schedule, like every hour, we would only want to import those records that are new or have changed within the last hour. There are several scenarios:
a.       Importing new / updated products
b.      Updating shipment tracking
2.       How can we flag records that failed to import so we can re-import them? If there is flag or field we can use (question 1 above), but something in the import fails, we don’t want those records updated as “already imported”, but rather remain either “not-exported” or “failed” so we can re-submit the request.