What sub-meter geolocation solutions exist and how can I integrate them into a web and mobile mapping workflow?

I am the manager of seven water systems. What I am trying to do is map out every meter and valve on to a map and then my workers can have the maps on their iPhones so when they have to go fix a water leak or something they can just look on their map and know where the meter and the valve is.

I've plotted a few meters on my phone and then got the longitude/latitude and transferred that into Google Earth, but there are a few problems with that:

1. My phone is usually 10 or so yards off on my "current location". I need to be within a few feet to plot water meters.


2. It takes forever to take the points that I have plotted on my phone and key them into Google Earth.


3. Once they are on Google Earth my workers still do not have them on their phones so it does them no good while they are on the job.

So does anyone know of a much easier way to do this? I just need to plot the points very accurately and then be able to access the points from different iPhones and computers.