I checked my own, got approximate dilation as well as observing when the bag of waters was bulging at the end, and found when I was swelling upon early involuntary pushing and needed to hold back a while. Less intrusive than having someone else do it, and possible alone before being with a care provider.
If I left for the hospital when I knew I was in labor with baby #2 I'd have been there 26 of the 28 hours from first patterned contractions to birth. I finally moved past around 4cm about 22 hours into it with suddenly transition-like contractions. Would have sucked to get diagnosed ftp because of my normal labor pattern.
Cervical change is only one part of it of course, its a combo of contraction pattern, emotional/mental state, cervical change, and other less observable factors all move forward either in fits and spurts or in steady progress.