@Partiko is a a mobile app for steem, available for the android and iPhone. I've been using for about a month now, and I love its functionality and features.
If you've got an android phone, you can download Partiko for free from the Google Play store (connect via your phone, obviously).
If you've got an iphone, I imagine it's the Apple Store
What I like about @Partiko
It's very functional/ works smoothly.
When you first click on the app, your 'home screen' is basically your feed, displaying about one and a bit posts (if they've got pictures) on the screen. Basically it just looks like a perfectly 'normal' way of presenting a social media feed on a mobile app, and it's functional - swipe down to refresh and scroll to view through your feed.
Along the bottom you've also got trending (I think this is the normal shit), points, and notifications, more of those in a mo.
You've also got the pink 'write a post' button to the bottom left and your own 'profile' icon to the top right - if you click the profile link, you get to see your basic data and you can claim your SP rewards via it too!
You don't need to actually click on one of the posts in your feed to upvote or resteem it, but you do to read it (which you kind of might want to do before voting it, but then again, this is steemit and who actually fucking reads anything - I'll give 1 SBI to anyone who references this sentence in the comments btw, just a little (tangent here) tester of readership).
EDIT - UP TO 8SBIs now and almost out of liquid steem, so this offer is now over! I guess this is a good sign!
If you do click on the post to read it, you get further 'link buttons' - to share via various social media, and a link to view the post on steemit.
I use it mainly for voting and commenting, but the posting function looks perfectly usable too - it allows you to add photos, so I could see myself using it if I didn't have a lap top handy.
Partiko has the best 'who voted for me' display...
I love this feature... If you click on the 'number of votes' under any post, you get the following display...NB - not the above user's or my own voters.. just someone random I picked from my feed...
The voters are ranked in order of vote value, with the weight they used displayed in a pink circle around their profile picture (100% weight = full, 50% weight = half circle)
There's gamification via the points system
You get points for voting (5), commenting (10), posting (30) and even 'checking in' (10).
There's also a leaderboard, although I don't think there's any honours for getting to the top of it, the main point of points seems to be that you can redeem them for upvotes from 
As long as you use the votes and comments with a level of integrity, this I think encourages engagement.
It's a great way of getting notifications on your interactions
Having turned off the alerts on my phone (I don't want it buzzing every five minutes) I found the notifications stream to be really useful.... very usable and it allows me to click on the notification and reply to comments for example. The notifications includes mentions too.
The development team seem to be really on the case!
Since this initial 'Announcing Partiko' back in the spring of 2018, the team have clearly been busy, having achieved all of the aims talked about in said post and since churning out even more new developments with the app, the latest being a 'promo option', which they're currently utilizing to promote steemfest3.
There's also a nice 'Easter Egg SBD Giveaway competition which the team run every time they produce a new release of the app: the team doesn't announce every feature change, they let users find them and give away SBD to those who spot some of the unpublicised changes. The winners of release 4 are mentioned in this post, for example.
NB - It's worth noting from the above post how the developers are constantly calling for feedback from the users.
Downsides
ATW there is a slight problem with the 'timeout function'... sometimes when I vote or comment, I get a 'timeout message', but everytime the vote or comment has been registered. Not so much a problem with voting, but once I put the same comment three times under a post thinking it hadn't gone through the first two times.
The notifications links only take me to the post, not the actual comment, which means (potentially) a lot of annoying scrolling down.
It's not so much a downside of the app itself, more of my own (irrational) use of 'gamified' tracking tech in general:
The app is encouraging me to only upvote and comment via Partiko, because of the points, even when it's not necessarily functional for me to do so.
I also initially found myself giving multiple people 5% upvotes, to try and advance up the leaderboard... I got over it pretty quickly, but the leaderboard function at least is very much open to 'shilling', or whatever the correct term is... posting multiple shit comments to progress up it!
However, I'm sure it'd be easy enough to change the way points are awarded to prevent abuse, and given how on the case the dev team are, I'm sure that's coming!
Final Thoughts..
Now I've got over the urge to 'game' the leaderboard, and only use the app when it's functional to do so, this really is a great way to access steem on yer mobile device.
NB Some of the 'downsides' may already have been corrected by the time you read this! There might even be other features I've missed, you can always comment and add them in if that's the case...