I also wanted this, and yesterday I worked on it. I made a simple working prototype that displays the time of the current task.
https://github.com/Mice7R/i3status-rust/tree/issue_1703_timewarrior

The block has two options: interval and format. And the formatting accepts: icon, elapsed, tags, annotation.
It's just a prototype right now so everything is subject to change.

Take a look at it @notramo and tell me what you think. I'll make a PR once I clean the code a bit and add docu and maybe add something else.

@Mice7R, thanks for your work. I haven't been able to test it, because I couldn't compile it (Void Linux currently ships Rust 1.64, which is unable to compile a dependency).

Could you also add stop/continue functionality if it's not too difficult? Clicking on the block would stop the timer if it's running (timew stop), and continue with the previous tags if it's stopped (timew continue). It could shell out to the timew executable.

How does the block behave after suspend/resume. Does it need any special code to handle?

I've been using it myself today and I will add the stop and continue, I also find it useful.

As for the suspend/resume it uses the task startdate to calculate elapsed time, which is the same behaviour as timew. If you want for the time to not count whilst suspended you'll have to stop the task before suspension.

I've been using this for a few months already and I kind of forgot of this issue. Anyway, I've added the missing documentation and made the PR #1878 .