Before you put your trust on some gadget, here are some ways technology can let you down from recent news and how they can interfere with location-based technology including GPS satellites and its signals:
CNet reported on a study by NOAA on the effect of solar eruptions occurred last December and its accompanying radio bursts had on GPS signals.
[Update: And today NOAA released a study pointing out that a new cycle of sun spots is likely to start around March 2008 peaking up in 2011. Via CNET.]
DARPA's Backup System
Boeing is developing for DARPA the concept of a non-GPS based system named Robust Surface Navigation (RSN). From the PR:
"[the] program is to develop technologies that can exploit various "signals of opportunity" -- electronic waves emanating from satellites, cell phone towers and even television transmission towers -- to provide precise location and navigation information to ground troops when GPS signals are being electronically jammed or blocked by natural or man-made obstacles, such as foliage or buildings."[Update: Rosum will be working with Boeing on this project, providing its GPS over TV signals technology. Via NewsFactor]
Today Tech.co.uk pointed out a study from the Swedish Defence Research Agency saying that CPU's running at close range to a GPS receiver can interfere with its accuracy.
Unreliable Location-based 911
And the San Jose Mercury News published an article on the study being developed by APCO on the reliability of location-based information provided by 911 services over cell phones.
GSM networks are known to provide poor resolution while CDMA provides a much better accuracy by the nature of its own network (time-based signals).
Shirt with GPSOverIP
But that won't stop someone to dress for the occasion with a shirt that transmits your current location using GPSOverIP and comes with its own data plan from Vodafone.
Keep your maps around, you might need them.