It is unclear for timezones behind UTC. If you are in UTC+1, the leap second happens at 1 am, so the countdown would be over: no fun here. If on the other hand you are in UTC-1, the leap second happens at 11 pm, so if the countdown clocks are not corrected for the leap second, friends can still be annoyed.
Either way, your friends will be annoyed..
What clock is set that precisely, hasn't drifted since being set, and won't pick up the correction by itself?
A GPS watch without a firmware update to handle the latest leap second?