I bought an Auterra about a year ago for use on my Honda and have been happy with it. I haven't tried it on my Titan yet.
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This company sells on eBay for slightly less than on their web page. I paid around $165 plus shipping.
If you don't already own a Palmpilot, it probably isn't worthwhile to purchase one just for this purpose.
If you want to use a laptop instead, have a look at this one:
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But, in my opinion, their software isn't that good.