Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
I assume you mean 'reliable' in 'free from breakage and failure', rather than 'providing accurate locations all the time' ?
...But I'd rather wait to hear what reliability factor is most important to you, before answering, if you don't mind just giving me a little more info, by the Reply To Expert function, please.
I think it's safe to say that the Garmin Nuvi line has very good reviews.
(Also, Garmin Nuvi products are rather easier to 'treat' [i.e. procedures less than repair, for faults] than other lines of GPS such as Magellan, TomTom, Mio, etc.)
Do you need more specific information?
A tracker, in other words.
I actually met and talked to an entrepreneur developing automotive trackers, but my overall knowledge of them in the entire field is not extensive.
So I feel it's best that I open this case to other Experts, one of whom might have broader (even if less close) acquaintance with the field of tracker devices. I have Opted Out, opening this case to other Experts in this category.