"Update me!" nag message

When I fired up Xonotic yesterday, a little yellow bubble started floating around telling me to update. The game was still playable, but it was enough of a distraction that I will update pretty soon.

Could anyone outline a bare-bones way to add this to vanilla Quake? Something that nags a little but leaves it to the user to download. I imagine something like checking "http://mygame.com/version.txt" for a match. If it doesn't, centerprint the content of "http://mygame.com/upgrade_message.txt" every few minutes.

xonotic being a multiplayer game with csqc, the server can just send a version number that way, with the csqc displaying pretty much any message it wants, possibly even with pretty pictures.
such messages are annoying in single player.

the key thing is to not nag players when they already have the most recent version... so if you were to do it with a file download, you'd need to include the current version as part of the url or some such.

personally I'd add some message just above the hud for the first 10 secs of each map or so, just something like 'new $engine version available!' or some such.

Good point with the multiplayer. Can the master servers also send messages? When I played, the message came up after seeing the sever list and before connecting to a local server.

Thinking of single player, or connection to a vanilla server, the client would have to do the checking.
I'm going to check out tutorial/discussion here... is it straightforward to download from a specified http or ftp address? viewtopic.php?f=12&t=1669

The address might be set by a cvar