I have used TomTom One then XXL. These devices (XXL is a Nav2 series) had route planning on the device and especially off device using the excellent 3rd party prog 'Tyre'.
It was possible because TT used an Itinerary file .itn This text file was a list of waypoints.
The file could be created by TomTom Home (but only start/destination points) or a complex route with many waypoints, using Tyre. The progs transferred the itn files onto the TomTom device and were available by menu.
When Nav3 was introduced, itinerary planning was abandoned.
When Nav4 was introduced it partly revived route planning so that it is possible to manually add 'destinations' to a simple route but only via the device screen. I don't know how easy it is to add or how flexible.
Having built a demo route plan on a Go600 in at my local SatNav retailers, we failed to save/or load any routes.
TT support confirmed (Feb 2015) that it is not possible to build a route on any external device (PC, tablet, etc.) and load the route onto the new (Nav4) devices.
Tyre have not stopped supporting TT devices but Nav3 and Nav4 devices do not have any feature to load/save a route files.
So it appears that Tyre is not compatible with new devices when in fact the new devices are missing the necessary route planning tools.
It was possible because TT used an Itinerary file .itn This text file was a list of waypoints.
The file could be created by TomTom Home (but only start/destination points) or a complex route with many waypoints, using Tyre. The progs transferred the itn files onto the TomTom device and were available by menu.
When Nav3 was introduced, itinerary planning was abandoned.
When Nav4 was introduced it partly revived route planning so that it is possible to manually add 'destinations' to a simple route but only via the device screen. I don't know how easy it is to add or how flexible.
Having built a demo route plan on a Go600 in at my local SatNav retailers, we failed to save/or load any routes.
TT support confirmed (Feb 2015) that it is not possible to build a route on any external device (PC, tablet, etc.) and load the route onto the new (Nav4) devices.
Tyre have not stopped supporting TT devices but Nav3 and Nav4 devices do not have any feature to load/save a route files.
So it appears that Tyre is not compatible with new devices when in fact the new devices are missing the necessary route planning tools.