The first try was the German site wetter.com. They offer a free API for small projects and the system seems to be very secure in regards to misuse of one's credentials by someone else, since a secret key and the search string are needed to create an MD5 hash which is then used as the actual query URL.

Unfortunaltely, the offered features are very limited. Only ery basic information about the current conditions is available. Not quite what I am used to from my Android phone.

So I am currently looking into what wunderground.com has to offer. And that's a lot! Again, for small projects their information is free (as in free beer). Small means less than 500 requests per day and less than 10 per minute. Both shall be very, VERY acceptable for me. Once the system is in place I will probably update once an hour. Maybe less.

What bugs me is that the query URL only consists of unencrypted commands and an unencrypted user specific key. So basically anyone who gets hold of this key is able to poll information on my account. Which could in turn get me into trouble since it would be seen as a valid request. The wetter.com authentification scheme is a little bit more difficult to use but would give me some more peace of mind.

Anyway. Since I am only planning to install the system in my own home and won't use it on someone else's network I am probably okay with it and prefer wunderground.com because of the more sophisticated features (hourly forecast, sattelite images, the lot!).