Limit Call Duration

[#1]

Does anybody know of a device I can get to plug in to my phone line to automatically hang up a call after 1 hour to stop my wife from talking too long and running up call charges...?

[#2]

If the wife is for this project then a kitchen timer by the phone should suffice to let her know when say 55 mins are up. If not I wouldn't like to be in your shoes if she gets cut off just as the  is getting interesting. 

[#3]

I haven't found anything on sale in the UK but there is a device called "MAX CALL TIMER" on sale in the States. I think there might be quite a few people in the UK who would be interested in a similar device if the price was right.