I liked @KyleMit's answer on how to make an unstyled input group, but in my case, I only wanted the right side unstyled - I still wanted to use an input-group-addon on the left side and have it look like normal bootstrap. So, I did this:
css
.input-group.input-group-unstyled-right input.form-control {
border-top-right-radius: 4px;
border-bottom-right-radius: 4px;
}
.input-group-unstyled-right .input-group-addon.input-group-addon-unstyled {
border-radius: 4px;
border: 0px;
background-color: transparent;
}
html
<div class="input-group input-group-unstyled-right">
<span class="input-group-addon">
<i class="fa fa-envelope-o"></i>
</span>
<input type="text" class="form-control">
<span class="input-group-addon input-group-addon-unstyled">
<i class="fa fa-check"></i>
</span>
</div>