RTC for Marlin?

I am interested in having a hours of operation for the printer - just something that keeps track of how long the machine has been operating (i.e., executing g-code.)

I can solve the problem for $14.95 with this

However, this adds weight and needs space on a panel somewhere, etc. So I thought why not have Marlin keep track and display?

A DS1307 real time clock (RTC) board is only $2.50 on ebay. It hooks up via I2C.

Any interest? Has someone already done this?

Interesting - but how much accuracy do you need? If you're content with a bit of drift, then it may be possible to add something to the firmware that will log how many clock cycles it's been through then update a counter every time it rolls over (with some scaling to get it into hours/minutes/seconds). Store that in EEPROM and you've got an hours counter without adding any extra hardware or cost, add a command to retrieve the counter and you've got the basics, or maybe have it report the time every time it's updated (so every hours/tenth of an hour/minute?) so the program can show the rolling display