I just buttoned up the first powerhead, a milestone

Im wondering far into the future that Im going to want to track the exact usage on these sweethearts.
Has anyone hooked up an hourmeter to their 50's 60's vintage outboard motor? What should I look for that will work with the magneto ignition?
I did see a type on ebay that wraps a wire around the plug wire, but this would be unacceptable to me. These motors are/will be at "museum quality" and I dont want some extra wire hanging around the spark plug lead that I'll need to explain every time someone sees it. (and yes, I'm going to use these babys and the boat, up on Lake Erie)
Thanks for reading....
HELP / any ideas?
Rob