dojaviti

1. (+ dat.) to report; to notify; to tip off
   Neko je dojavio policiji gde se krije. — Someone tipped off the police about where he was hiding.
2. to let know; to pass on
   Dojavili su nam da je pošiljka stigla. — They let us know that the shipment had arrived.

Construction: dojaviti kome (dat.) nešto / da...; the related noun is dojava "report, tip-off". The verb sounds official; for personal messages ("let me know when you arrive") javiti is normally used.