Query approved and moved.

I use GMaps as well as the Bing Maps on my Windows phone.
Plus, there is a handy tool - GPS Voice Navigation. (available for Rs 299)

For the GPS Voice tool, you can simply plug an earpiece and ride or let the pillion handle it and guide you.
GMaps are fairly accurate. Bing is also good. Chennai maps were better on the Bing though!

1. See, maps may have inaccuracies due to these reasons:

a. some new construction that happened meanwhile,
b. the destinations (shops, restaurants, businesses, etc.) on google maps may turn out wrong as they're contributed by people themselves.
I noticed this during my college picnic preparation, whereby "Angel Resorts, Jaipur" was told by Google Maps, to be in the Jaipur city, around S. K. Soni Hospital. Reality was that it was beyond Harmada Police Station, outside the city.
c. Some natural calamity or accident may stop you from proceeding on a particular route, even if its listed as correct online.
d. Places with multiple names, like there is a Srinagar near Ajmer too.
e. Listing a place as land or water, may be wrong in the maps. That water may have dried up, essentially allowing you to go through a smaller route through the water body. This might not show on GPS.
When I was on Sambhar lake's salt flats, GPS showed that I was in the middle of the water. Probably because the lake might have dried up over the years.
That said, GPS is generally reliable if you know its demerits and do some research on the area you're visiting too.

2. Well, on one trip to Neemrana fort palace, Alwar, where I got lost 2 times, GPS saved me. On another trip to an unknown place in a cage with family, GPS helped me a lot to find the actual destination. So, GPS does help and there's no doubt about it. But your device must have enough battery life for it.

Conclusion: Keep your phones charged, keep the GPRS/ internet access ready, do some research on the area you're visiting, and GPS will prove itself.

3. Google maps is the most famous. But, you can search for "Route 66". Also, "Co-Pilot" and "Waze" are some other apps...

Have a look here for their comparison: Ultimate GPS showdown for Android | Android and Me

I use Nokia maps on my Nokia C7 as a gps navigation system. Not upto the mark sometimes.. its always better to confirm if you are not sure. But the good thing about the maps is that you can see whether the next turn is a dangerous 'u' turn on the ghats! and alter the speeds accordingly..

what about GPS devices for motorcycles?

Has anyone used this: TrailBlazer for bikes: GPS Navigator and Car Entertainment System from MapmyIndia

I am looking for one so kindly shed some light

I do carry a GPS enabled phone with Map My India.

Its been almost two years. I am yet to use it

In India rather than checking the GPS, I find it much more convenient to ask some friendly person directions. So far that is the best!!!

I use a road pilot which is any time available in my bag irrespective of my travel mode, I carry a regular charger with universal pin / USB Cable / Chineese made AA battery universal charger

This has helped me in many of the occasions, I also use Google maps occasionally on my BB / Nokia phones

Nothing to beat the living GPS (People), they can help you where ever you go, these devices may be useful where you can find nobody out to help.

This is just an other gadget which makes us lazy at times & we forget to socialise in many of the occasions.

My paternal uncle had done 2 rounds across all states in India, he only carried a paper road map in the 80's to do that and again in 2009 he went without a map.