neilgee

This plugin adds support for placeholder text in browsers that don’t support this HTML5 feature including Internet Explorer 6.
The plugin just activates the placeholders.js script by James Allardice http://jamesallardice.github.io/Placeholders.js/
There is no further configuration required.
For HTML input elements use the placeholder attribute and add a value, this value is removed when a user inputs the field. http://coolestguidesontheplanet.com/add-a-label-into-a-text-input-field-in-a-html-form/#html5
The script is 4KB and is set to load in the footer and has no library dependencies.
<h3>Usage</h3>
Just activate the plugin which loads the script, their is no further configuration.

Placeholder Text

This plugin adds support for placeholder text in browsers that don't support this HTML5 feature.

Tom Baumgarten

SCF is a simple plugin to create inputs for your forms with the same style everywhere, in your plugins or your theme. This plugin manages many fields so that they are efficient, accessible, versatile and homogeneous everywhere. A lot of options and multiple hooks. Made by developers, for developers. 
Compatible with CF7.

Simple Coherent Form

A simple plugin to create coherent inputs between themes and plugins. Light, efficient, accessible and compatible with CF7. Best for developers.

Placeholder Text vs Simple Coherent Form