Invoke a send email dialog box or form for a selected grid item(s). Native solution or code?

Hello Paul, depending on the complexity of the use case, you could use a native approach. 

You could have a formula url button that will edit the record uncheck a box, then edit the record again checking the box. this check box event can trigger your native email notification as the condition. 

The subject and body can use markers from the record. 

I would even make this button use the Growl method, so that you did not have to redirect from the page. Here is an example of a Growl Button I created with a rich text formula field. In my URL, I am only making one edit call, but I am editing 2 fields.  

var text Update= If([Checkbox]=true,URLRoot() & "db/" & Dbid() & "?act=API_EditRecord&rid=" & ToText([Record ID#])  & "&_fid_17=false&_fid_23=Checkbox Toggled to False",URLRoot() & "db/" & Dbid() & "?act=API_EditRecord&rid=" & ToText([Record ID#])  & "&_fid_17=true&_fid_23=Checkbox Toggled to True");

var text URL = 
"javascript:" &
"$.get('" & 
$Update & 
"',function(){" &
"$.jGrowl('Checkbox was toggled', {life: 5000, theme: 'jGrowl-green', header: 'Important'});" &
"});" &
"void(0);";

"<a class='Vibrant Danger' href=\"" & $URL &"\"" & ">Growl Button" &  "</a>"



Let me know if this helps, or if you have some questions.