Navigation indoors. Existing solutions

GPS
As far as I know, indoor GPS on patenting ideas GPS repeaters has not moved. However, someone promisesthat SiRFstar V technology SiRFusion by the end of 2012 will work in the premises. But such promises are heard for a couple of years, and working chip is not...
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\rWi-Fi
As for Wi-Fi, the options are many:
\rEkahau is perhaps the most known commercial Wi-Fi system.
\rawiloc — Fraunhofer Institute.
\rWalkBase
\rNavIndoors
\rPlace Lab (Wi-Fi + GPS + GSM) is quite old (2005), the Intel prototype, open source.
Note that to get any decent accuracy Wi-Fi system should be periodically calibrated, since the signal strength over time, floats, and positioning accuracy decreases.
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\rOther:
\rUbisense accuracy to 15 cm, but not Wi-Fi (requires additional iron) and costs about 10-20 euros. If money is not a problem, it is, in my opinion, the best option.
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There is still GloPosthat based on GSM data promise an accuracy better than 12.5 m But "independent tests" that they reference is not really confirmed.
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Positioning system based on FM radio does not require infrastructure receivers is already in the bunch of mobile devices, but the commercial FM systems has not yet matured...

Like wrote here about the latest SurfStar, I don't remember which number, there will be support for the move, try to dig in the wrong direction.

www.indoorlbs.com/ — I suggest you read, there is useful infa!