Hey,
woutervdm, its a great idea, but your website is crap and there is many other things like this. Why would I choose your service over other peoples?
Now for some constructive feedback: Add some unique features that would make people want to use YOUR website instead of others. For example, charge a few cents or 0.001 BTC a day for text notifications. Many people don't have access to wifi or 3g all the time (like me) so I would love a SMS notification that would get to me no matter where I was. Email notifications should definetly free, but if you want to make some money out of this, charge for some features. For example, you could make a 30 minute delay for a price notifier for email, which is free, but then you could pay 0.001 BTC to get instant (as instant as email can get) notifications.
On a side note, oh crap litecoin and bitcoin are crashing. Litecoin is at $18.9 and btc is at $653. Thats just fantastic