Does anyone know a lightweight app that will maintain gps lock when the phone is locked?

I need for google maps to be almost instantaneous when opened. It takes a good 15-30 secs from standby to get location.

I can run a background app like sports tracker and this achieves the purpose as gps lock is maintained when the phone is in standby. However, it tends to be a fairly battery intensive app due to the constant data recording.

Can anyone else suggest another app that runs in the background and would achieve this?

Latitude is a possibility, but Id prefer a more private solution