Let's say I want to monitor the price of 0.5 btc in Japanese yen in coinbase as well as the midmarket (XE) price. So it would display live update of the exchange rate of 0.5 btc in yen in coinbase.
If you drop the "0.5 BTC" requirement and it's fine for you to see the price for one entire coin, you can use the widget I am using.
It's far from perfect, but it does the job.
You can choose the coin (not only BTC), the exchange (coinbase, bitstamp, ...) and pair (BTC-USD, BTC-EUR, ...) and another currency you want it converted to (JPY). I am not sure it uses XE for conversion, since it's not my widget, still you can give it a try and see if it's good enough for you. https://play.google.com/store/apps/details?id=org.phauna.litecoinwidget
I'll add that unfortunately sometimes it has entire hours when it's not updating at all. But that happens rarely enough so I didn't give up on this widget yet
