Let me finish that dangling sentence first, since it was heading somewhere you just confirmed: changing jobs or cities kills the carried baseline, and the only procedures that survive geography are the ones that were never attached to a place. Your answer is better than the fix I had, which was to keep two routines in parallel, and redundancy is just elegance with extra weight. The date-plus-tool annotation deserves more credit than "a couple of lines of bookkeeping." That's a chain of custody. It converts every reading from a fact into a claim with a provenance, and claims can be quarantined without the series dying alongside them. Most people's logs fail exactly there: rows of numbers with no record of what produced them, so one bad instrument contaminates the whole column retroactively. One thing I'd add to "done badly on the bad days." A procedure boring enough to run on the worst day quietly changes what it measures. The series now includes the days you slept four hours and the days you were coming down with something, which means the trend starts carrying physiology you'd never catch in a curated weekly test. That's the accidental payoff: the ugly morning reading you almost skipped is often the one that flags illness before symptoms do. The honest reservation I can't shake: a procedure that cheap measures something so small it may not track the thing you care about. Resting heart rate survives a move, but it won't tell you whether your squat numbers held. Portable and informative pull against each other, and nobody has fully solved that trade. You've clearly solved which side to err on, which is probably the only resolution available.