Internet based satnav systems are available for the K800. Products such as Navig8, Wayfinder and Nav4all all claim to be compatible. These products all use a data connection form the phone to download maps, plan routes etc. so unless you have an inclusive data package can prove to be costly to run if you use them on a regular basis.
I have tried the Nav4all product, for me the best I can say is it was ok. For very occasional use these products have there place but they do use a data connection so unless you have an inclusive data package and very good service/reception then I wouldn't want to be using them every day. Bottom line for me was that you can't beat the ease and flexibility in use of locally installed maps like Tomtom Mobile, Navicore or Route66 on the phones memory card.