Also the 'main' box where you enter height and weight can I think be made much nicer looking with a few small modifications, I think it's important for you if you want others to put your widget on their site. The numbers in the stars are too big and not properly centered, the stars themselves are too big, the alignment of all elements is off (text not centered, button not aligned to other elements, no padding in the box title, bottom padding too big or not in balance with other padding).
All of this from somebody who doesn't know anything about design so I may just be talking out of my ass here.
I have mixed experiences with getting design off odesk/elance-like sites, and I'm a cheapskate and afraid to spend money on my own products without being sure that it will pay itself back. Which is a self-fulfilling prophecy because crappy looking things will sell badly, too.
Anyway I'm quite impressed how you're coming up with multiple ways to spin such a basic thing like a BMI calculator. I hope you will find ways to make this work and make money for you.
thanks for the detailed critic :-) It's true I'm a software developer and design is difficult for me. I've noted your points and will try to address them with my designer.
BTW, are you dutch (your name)? I'm French but am based in Amsterdam :-)
(In case it needs to be said: I'm not saying you made a wrong choice, I'd really like to know/understand why you chose to go this way :-)).
To justify spending 200 euros: 200 euros is really not much in the grand scheme of things and considering the above, I think it's worth the expense. When asking for links and you have a good looking site, your requests are more likely to be answered than if you have a garbage-looking site.
Regarding whether it's a wise investment of my time, it's harder to say. There's the time developing it but also (mostly) marketing it, link building etc. I think at some point you have to go with your guts, you will never have all the data you wish at the beginning. Then if it works really well, I can look into adding more features, more calculators, more content etc...
In my mostly-unqualified-to-comment-opinion, that is.
I decided to spend a minimum amount of time on it to just test it out: just a form and a little description. The only decoration was that the text was centered and navy :)
Results: only 4 sign ups over 3 months..mostly from friends and family.
Then I made a nicer design, added content, and voila got about 30 sign ups in about 1 month through google search results. Added benefit is that now I'm not embarrassed to promote the site which of course has yielded many more sign ups.
To sum up: an effort invested in design pays off since good looks provide a hint of legitimacy. Generally speaking :)