Current:

I see three stages that need to be done, and only the first can be done for now
Sometimes wish iOS has a checkbox control
Luckily, there's OSS 鈽猴笍
https://github.com/Boris-Em/BEMCheckBox
https://github.com/Marxon13/M13Checkbox
Oh, didn't think of emoji. Nice one! Is there an emoji for an empty checkbox though? I can't find one.
Ha, I figured there was, but maybe not 馃槥
This would be lame, but maybe 猬滐笍 ?
Otherwise we'll have to do text location finding, could be a huge PITA 馃槵
Bit shit but with a large font size:
What about icon fonts?
https://github.com/dzenbot/Iconic :)
You could use a subclassed NSTextAttachment in the NSAttributedString. With a little bit of code, its possible to allow any arbitrary UIView.
That way you can still keep the string, but create a custom view easily.
(or even use a UISwitch or whatever makes sense)
Out of the box, only image attachments are supported, but if you google a little you'll find simple examples for how to achieve this. No need to import a 3rd party lib.
EDIT: Quick note, your custom attachment would NOT participate in selections, i.e. copied text will not include the attachment. You could obviously get around this by overriding the copy command and putting back the original [x] if you wanted. Currently however the app doesn't support this behaviour anyway.
Closing as this is working, filing a new issue for interactivity
Most helpful comment
Bit shit but with a large font size:
鈽戯笌鈽掆槓