For my current project, I needed a more robust character count that was was out there, so I started by looking at what Andrew Weaver had done with his, and came up with this offering.
MD Character Count will show character counts below textareas, text inputs, and MD Markitup fields in the CP. You can set character counts to “soft” (which is the default) which is more of a suggestion, or “hard” which will limit the field to that many characters and no more. You can also customize the message underneath each field.
You can download it from the MD Character Count page at Masuga Design.