Reboot if any updates were applied

You can grep /var/log/dpkg.log and perform logic based on the date / time your selected package name(s) were installed

You may want to compare that to the system boot time to see if it has been rebooted since the installation. You can see the date and time of boot with:

dmesg -T | head -n 1 | cut -d"]" -f 1 | cut -c 2-

SHould give you a solid starting point

grep grep /var/log/dpkg.log

may give this

2015-08-05 05:11:53 install grep:amd64 <none> 2.16-1
2015-08-05 05:11:53 status half-installed grep:amd64 2.16-1
2015-08-05 05:11:53 status unpacked grep:amd64 2.16-1
2015-08-05 05:11:53 status unpacked grep:amd64 2.16-1
2015-08-05 05:12:04 configure grep:amd64 2.16-1 <none>
2015-08-05 05:12:04 status unpacked grep:amd64 2.16-1
2015-08-05 05:12:04 status half-configured grep:amd64 2.16-1
2015-08-05 05:12:04 status installed grep:amd64 2.16-1

You can then use awk, cut and grep to hack the dates out and compare. Was your package installed after the reboot, if so then reboot

Using grep and awk is a very poor solution. Such logic is actually hard to implement, as log output is not well documented, and rather brittle, if the log messages happen to change in next version. Is there no other way?

What would be a better solution in your opinion? The logs show exactly when packages were installed so grep and awk are ideal here as the logs are text.....

I already explained why a grep/awk solution is never ideal.

A better solution would be something programmatic, like some hook. For example, a special file is created to indicate that the system needs a reboot after an update. I could not find anything in the documentation though about any indication that something was updated, or that some script should be run after an update.

If there is no proper implementation, it is best to acknowledge this fact. I would then create a bug for an enhancement.