1) Yes, iGuidance 3 can be used on your Cingular 8125 and Laptop running Windows XP/2000.
2) No, any Bluetooth GPS receiver included in the OCN6 are not "locked" in to one application only. Instead, the same Bluetooth GPS receiver can be used on any NMEA compatible GPS software such as top maps or other GPS tracking software (marine or aviation).
OCN6 vs. iGuidance 3
Pros:
1) OCN6 does not require installation, building maps or copying of maps. It's plug and go with the pre-programmed memory card included.
2) OCN6 has a more POI listings, from 3.5 to 12.5 millions packages vs. around 2 millions in iGuidance.
3) OCN6 has smoother 3D map view with the ability to tilt or adjust the 3D viewing "Angle", and the 3D also provides smart ZOOM feature.
4) Easier to search for POI in OCN6 vs. iGuidance. In OCN6, you can search for many retail chain stores such as Best Buy, Costco, Walmart, Staples, etc or simply type in a search keyword in the POI category to search all POIs listings. This is a very useful feature if you do not know which category a specific POI would be categorized. In iGuidance, you cannot search POI in the main category. You must go into each POI category and try to perform a search.
For complete POI categories available in OCN6, please see: http://www.oncoursenavigator.com/forum/default.aspx?f=10&m=5541
5) OCN6 has customizable status bar: Improve readability by customizing your status bar to show only the information you need. In iGuidance 3, you will have to tap on the status bar to see ETA, Time to destination, Distance to destination, one at a time vs. all 3 at the same time in OCN6.
6) OCN6 has smart keyboard that hides out / disable characters that does not apply to your currently search street, based on the current street and city you are entering.
7) OCN6 has Smart Power Saving feature allows OCN6 to temporary overwrite the PDA/phone settings to keep the device always on when navigation program is running and iGuidance has none (or rely on your PDA/Phone's OS setting
8) OCN6 complete seamless / connected USA and Canadia plus Hawaii and Puerto Rico maps take up only about 950MB vs. 2.4GB in iGuidance 3.
Cons compare to iGuidance 3 (features as of writing and does not include any new features that will be introduced in 3.1x)
1) OCN6 can only be used in PDA / PDA Phone but iGuidance 3 can be used on both Laptop/PC as well as PDA/PDA phone.
2) OCN6 does not have the ability to tell you wish side of the street your destination is located vs. iGuidance tells you that.