Not really like you want, but you can put in your cron.
@daily uptime
@daily w
And by mail to your user or you can tell cron to which user send it will send the outpout of that commands... say some like:
w
09:19:23 up 3 days, 1:38, 1 user, load average: 0.02, 0.12, 0.13
Maybe it works for you.
Ah, I need to point that Debian had done a very good job tweaking cron, so there are some ways to put easier crontabs, from man 5 crontab:
Instead of the first five fields, one of eight special strings may
appear:
string meaning
------ -------
@reboot Run once, at startup.
@yearly Run once a year, "0 0 1 1 *".
@annually (same as @yearly)
@monthly Run once a month, "0 0 1 * *".
@weekly Run once a week, "0 0 * * 0".
@daily Run once a day, "0 0 * * *".
@midnight (same as @daily)
@hourly Run once an hour, "0 * * * *".
Now that you mention, if you want to know when the server you are reboots put a echo "I been restarted" on a crontab @reboot :D it's a nice way to know.