HAZOTA

This plugin publishes a simple endpoint at <code>/kmut.txt</code> on your site to expose your account identifier for seamless integration with KissMyUpTime’s completely free uptime monitoring service.
A <a href="https://kissmyuptime.com" rel="nofollow ugc">KissMyUpTime</a> account is required, and you can create one for free – no personal data required.
KissMyUpTime offers a real-time interface and instant notifications across all your devices, along with precise uptime percentage calculations, an unlimited number of checks, boostable intervals, and multiple nodes around the world.

KissMyUpTime

Helps you easily integrate KissMyUpTime's completely free uptime monitoring service with your WordPress site.

Sandy McFadden

This is a very simple plugin which requires almost no configuration.
All you need to do is go to the Appearence then Widgets area in the Admin Dashboard. 
Once you are there drag the BMI Calculator widget onto the widget area you would like it added to.
The only two settings are the title and the color. The color is the hex color you would like the results background to be.
A lot of the code was adapted from 
<a href="http://codereview.stackexchange.com/questions/21581/calculating-body-mass-index-bmi" title="Inspiration Code" rel="nofollow ugc">Stack Exchange Thread</a>

Healthy BMI Calculator

Adds a shortcode and widget that will display a simple BMI Calculator on your site. Works with both metric and US style measurements.

KissMyUpTime vs Healthy BMI Calculator