I don't care about mobile friendliness in a browser so much. I'd rather have a one tap app, instead of having to: open browser, navigate to the page, login, etc.
If it helps.. your are logged in for a month, so you don't have to bother logging in again. Just directly goto your bookmarked url or
pin the bookmark to home screen. Our mobile site is really optimized so you shouldn't feel much of a difference from a native app
Anyways, I understand ur preference for native apps. It will take us some time/resource to build a good looking android app. Yes, Sentinel looks good !
I don't like sites like this because I think it's bad practice to give one site a list of addresses that you own, they can be connected and it lessens your privacy.
We have ways to mitigate privacy issues. You can keep using guest login and are not required to use your own emailid. Also you can add extra dummy addresses to mask the addresses you really control. Of course, it wont give u the level of privacy from native walllet or bitcoind.