Google releases 'My Location' for cellphones (w/ google maps)
venturebeat.com
venturebeat.com
https://loopt.com/loopt/phones.aspx
More are on the way :)
Standalone is the type of GPS you are referring to where the phone uses only the onboard GPS receiver. This type of fix is slow and generally does not work indoors. It also uses a lot of power. When you get a fix, it's usually pretty accurate, but you don't often get one. Generally only iDen (Nextel phones) support this.
Mobile assisted fixes are where the phone gathers all the data it can (GPS satellite signals it can see, current cell tower and signal strength, etc) and sends it to a computer run by the carrier that does the actual math. This type of fix is really fast, usually works indoors with good accuracy and uses the least battery. It is however more expensive for the carrier computationally.
Mobile based fixes are when the phone uses almanac data from the carrier (which GPS satelites should be visible, the location of the current cell tower, etc) to calculate the phone's position. It only asks the carrier for new information every few hours. This type of fix is reasonably fast, frequently works indoors, and is fairly accurate.
Finally there is cell tower information which works instantly and is almost never acceptably accurate. It is not related to GPS at all.
Loopt uses whatever is available in order of accuracy. We prefer mobile based and assisted fixes (available on almost all CDMA devices released in the past 2-3 years), and fall back to standalone GPS and cell tower only when necesssary.
Users who mainly get cell tower fixes are usually not satisfied with the accuracy. We do our best to do better than cell tower, and so far have not released on any devices that only support cell tower.
I hope that clarifies things a little.