Electric hour meters are usually through an oil pressure switch. My L5740, key on listening to the radio, no hours. Leave it idling while I work outside the tractor, it accumulates hours. The old style "hours at xxxx rpm went out when they invented electricity. The 806 Farmall we got in 1963 was that way but the 70's and 80's Farmalls my nephew still runs have electric hour meters, all of have long ago bit the dust. My RTV 900XT, however, has a key on hour meter. Right now I estimate true hours by subtracting 83 from the actual meter reading, and my wife and I now make it a point to toss the key in a cup holder every time we shut off the engine.
Back to specifics, routine service is one of those things that make a nice penny for the dealer without costing him much. There's no real downside for him, so it's a nice thing to include in tractor purchases. Bargaining is all about finding things that are more valuable to one party than the other.
For example, the dealer probably has his own money tied up in the new implements on his lot, but very little in the used ones - and used ones work pretty much the same as new ones.
Most dealers rent implements and there's something with a real negotiable value. Along those lines, I know of one dealer who has keeps some "loaner" implements for the use of people who buy his tractors....but you do have to ask. That's a powerful negotiating tool for him, and probably not unique to his dealership. Certainly worth asking about, though.
It could be a separate device or maybe a mod to the existing instrument. The "intellipanel" on my Kubota knows the engine rpm, PTO rpm, operating time, and how to do basic arithmetic. It can display basic diagnostic data (and nag me about service) - which means it already has more than all the info it needs. It wouldn't surprise me to find that the intellipanel has an updateable chip...I don't know if that's true, but Kubotas does call it an "intellipanel", so at least the implication is there.
Does anyone know?
good luck to all those new tractor buyers out there
Not sure how much there is to the Intellipanel but the ECMs on most common rail Diesel engines contain a lot of information that can be accessed with the right computer software and connector. I mean things like engine hours, percentage of time in each of several defined speed ranges (1200 -1300, 1300 - 1400, etc.), percentage of time in a specific power band, highest engine temperature, highest engine speed (has it been oversped going downhill being pushed by a load for example), total fuel used, fuel burn rate. And most newer Cat equipment except the smaller building construction products transmits the major information back to the dealer and if the dealer is on the ball, they can call you and tell you a machine is being run while overheating or some similar thing. If your machine is stolen, they can also tell you where to find it unless the thief knows how to defeat the system. Beats the heck out of a meter that tells you 1,050 hours at 2100 rpm.