For anyone who reads this and is put off by the thought of having to update their system from source; there are binary patches available (both OS and packages) using the `openup' utility from https://stable.mtier.org/
MobileOrg[1] was good for a while—it had Dropbox and WebDAV support—but it hasn’t had an update in a couple of years and is badly in need of a new maintainer.
On OpenBSD the integration with physical devices is done via builtin software. I run a stratum 1 OpenNTPD server on OpenBSD, with a GPS attached via nmea [1]. The GPS data shows up via the sensors framework, which OpenNTPD interfaces with [2].
Not the person you asked the question of, but we’re building AMIs (and VMware images) using packer.io (via the masterless puppet provisioner). It works nicely and with a minimum of fuss.
I looked at inotify and quickly realised it was Linux only, which for me isn't a good fit as I tend not to be on a Linux box when I'm using my ssh client.