I was able to get this with the Samsung Focus. I did the Gather race and tried the dashboard thing after collecting all 8 arrowheads on the first lap.
At the end if the first lap just after completing the long turn and getting the last arrowhead, I pressed the back button which brought up the pause menu. After that I pressed the on/off button and let my phone sit for about 1 minute. When I restarted the game all the arrowheads had respawned. I did the same thing at the end if the second lap, because of time, I wound up leaving the phone idle for almost 30 minutes, and then completed the race and the achievement popped.
I don't know if it worked this time due to sitting longer than 5 seconds or because it was a gather race, if someone finds out, I will add it.
I assume this will also work for the Omnia.