App to measure distance, like between utility poles?

[SmittS]

I work with a telecommunications company and measurements between underground handholds and utility poles are often needed. Standard practice is to use a measurement wheel, but using the iPhone gps would be so much simpler. There are apps to measure between points on a map, but that isn't accurate enough and often the handholds or poles are new or not even visible. Anybody have an idea for an app for me?