Hi bobajobrob
Re the "mobile phone", I used to use a mobile for this purpose. Any Windows based mobile can run software and store maps that will allow this (like MemoryMap). I've used an HTC P3300 without much trouble, and it all works well on my current Samsung i780. The latter also uses Google maps which can provide routing. There are probably other phone OS that work too but I don't know anything about them.
However, the problem with using phones for this is the battery life is not sufficient for long rides and the weather and vibration resistance are not really adequate for the reliability you'd want. The HTC had various mounts available that allowed me to mount it to the bars but not all phones do.
Forget it basically.
So it's the "other device" that I'd go for. There's lots of relevant info in this section of the forum if you wade through. I can only really comment on the Etrex Vista HCx: it's a great job, probably better for routing than the 605 / 705, but the latter are better for training purposes, lap times and so forth, and they also permit intregation with heart rates / cadence.
