There's something called "automotive spec". It specifies things like temperature range, vibration, shock, humidity, power characteristics, EMC and other criteria that your in-car product has to cope with.

Auto manufacturers have to comply with this religiously - a factory fit stereo is bullet proof.

Mainstream after market manufacturers comply less rigidly, so some cool factor (or a price reduction) can comprise reliability slightly. Consumers are OK with this.

Niche after market manufacturers comply to differing degrees. With the hard drives available when the empeg was invented there was no way to meet the full spec, but the restrictions (mainly temperature) were published and niche consumers made the choice to live with them.

Hobby implementors usually don't even know what the typical automotive specification calls for, and neither do they care because they can fix something if it breaks.

This is one reason that it can sound so simple to pull a selection of parts from catalogues and specify the killer in-car PC. In practice it ain't that simple. It's a big, time consuming, expensive step from mp3mobile to empeg car and it's an even bigger step from empeg car to the mainstream.

Rob