Edit: it does seem to be available, even though Ireland isn't listed on their site by going to google.com/latitude on my mobile it installed and pinpointed my location. Quite impressive really.
There was a guy from google on one of the radio talk shows about 2 weeks ago on about it. It does work here but is not supported here. ie, if you get a location, great, if you dont, theres noone you can complain to.
I use latitude all the time. You have to go to google.com and not google.ie to set it up and use it. All my friends can type in my number and find my location at all times. (Really handy if your girlfriend doesnt believe where you are lol).
Hope this helps.
I use a nokia n95.
Couple of things, your phone has this info anyway, googles latitude app just interacts with it.
If you have GPS it will pinpoint you , if you dont it uses phone mast triangulation, the same type that you hear about in criminal cases all the time. The more masts in the area, the more accurate your positioning.
If youre worried about your girlfriend seeing you where you shouldnt be you can set a location, so if someone is looking you up, you can set the location to wherever you want and thats where theyll see you on the map. not sure if thats available for girls to set though.
I use it as a gps system with google maps (will need a datapack from your mobile providor) and find it very useful around dublin and country. nokia n51.