App engine app design questions
I think there are 2 options that would work for you, besides creating a entity in the datastore to keep  track of "last visited time".
One way is to just check the external page periodically, using the cron api as described by jldupont.  
The second way is to store the last visited time in memcache.  Although memcache is not permanent, it doesn't have to be if you are only storing last refresh times.  If your entry in memcache were to disappear for some reason, the worst that would happen would be that you would fetch the page again, and update memcache with the current date/time.
The first way would be best if you want to check the external page at regular intervals.  The second way might be better if you want to check the external page only when a user clicks on your page, and you haven't fetched that page yourself in the recent past.  With this method, you aren't wasting resources fetching the external page unless someone is actually looking for data related to it.
I want to load info from another site (this part is done), but i am doing this every time the page is loaded and that wont do. So i was thinking of having a variable in a table of settings like 'last checked bbc site' and when the page loads it would check if its been long enough since last check to check again. Is there anything silly about doing it that way?
Also do i absolutely have to use tables to store 1 off variables like this setting?