I tried Zeplin, Sketch measure plugin, and now switched to Markly. It's perfect for freelancer's work.

I want to say I am a happy customer. I got my copy 1 week ago, it's damn cool! I totally love the auto-updating concept. And, yes, the Sketch measure Plugin is also cool, but Markly really saved me much more time. :)

Would be nice to have a sample project or free trial period before purchasing.

That looks promising. But I'd love to use a demo before purchasing.

Apart from the cost Markly is decent. It seems much easier to use than sketch measure and Zeplin.

What I use in some cases is the sketch plugin marketch - does a lot well for free. https://github.com/tudou527/marketch

Looks pretty cool, I've been using this with no problems https://github.com/utom/sketch-measure

What other solutions are out there? I like the concept of Zeplin but haven't found it helpful with my current handoff process.

With PS I use Specking. Cost and simplicity is where this wins for me.

http://www.wuwacorp.com/specking/