Hi,

I spent a little time thinking of this project over the weekend.  There are
obviously two parts: Data Acquistion in the car, and Data Logging for
reporting purposes.

My thought was to design a box with two receptacles for Dallas Touch
Memories and a PIC inside (of course).  One receptacle would have a Dallas
device locked into it somehow, but easily removable by an 'administrator'.
The other receptacle would allow a second Dallas device to be inserted and
removed easily by the 'user'.  Four buttons would allow the user to select
the type of use that was being logged (business, personal etc.).

The point of using the Dallas devices are that there are versions that are
pretty much self contained data loggers.  Each user would have their own
(removable), and each vehicle would have its own (fixed).  When a user got
into a vehicle they would insert their Dallas memory into the box and press
the appropriate button for the type of use.  During the trip they could
change the type of use by pressing a different button, and at the end of the
trip they would remove the Dallas device.  The PIC inside the box would
handle data acquistion from the road sensors and date and time, and log it
in *both* Dallas devices.

Whenever the user has to produce an expense report, they apply their Dallas
device to a PC reader, which downloads the logged dates, times, mileage and
type of use from it.  The data may then be deleted from the device (or not,
some of them have huge memories).

Periodically the devices fixed in each box are removed, and downloaded by an
administrator.  This will allow a cross-check against all the trips recorded
by users' devices and also will allow administrators to see times when the
vehicle was used, but no user device was present, for example when the
vehicle was being driven for maintenance.

Just my $0.02.

Andy