>>When I turn on a panel, who do I check with to see if I need to update my data? What makes another panel's data more accurate than mine, or vice-versa?
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>get data from all active panels and process the transactions by time stamp?
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>when a new panel comes online, check for any new transactions?
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>normally, the number of transactions should by extremely low after the initial tuning. every unit must be tweeked for individual performance characteristics durring early after installation, then they should run for years with only minor changes.

This is an interesting problem and I know of no COTS software that addresses it (at least w/o a central database).
I imagine it wouldn't be overly difficult to code such an application. Have you considered this avenue?