You can request an API this way :
Code:
$.getJSON("https://min-api.cryptocompare.com/data/price?fsym=ETH&tsyms=BTC,USD,EUR", function(data){
console.log(data);
});
console.log(data);
});
You should note that this API is available using JS querries, but not all of them are.
Then you can add some style to a box displaying the price, and put all of this in a code snipet, it will result in a widget available every where, without any iframe.
It looks pretty good well done!