Looking for an app that will increase GPS refresh rates.

[MrTrauma]

I use my iPhone4 for mapping/tracking my routes but the refresh rate is way to slow on the the gps. Is there a tweak that will get the iPhone to check my location more fequently? I do have an external bluetooth GPS unit that I could use if I install the BTstack app... Would that work off the refresh rate of my external gps or the iPhone?