@naijaping @brainiacwebdesigns
I found the plugin by buddydev is full working and compatible with 1.5+ Doesn’t this suits your needs? Hope it does! 
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IMPORTANT UPDATE: Since a few pals here have tested and found some things to correct, I have addeded this correction (so now it works OK, yay!):
Below this:
<div id="message" class="info">
</div>
Add this:
jq('.pixelMonitor').remove();
jq(document).unbind('scroll');
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Hi, all, @naijaping @abysshorror @funmi-omoba
I finally found the time to work on this. I’ll post a detailed explanation on my blog later but here it goes for you to be able to use it right away. I’ll maybe make a plugin of all this, and some code you’ll have to tweak will be overridden if you update your buddypress theme but by that time I hope this will be improved and I’ll post to you back with the updates.
So:
1) Edit the file: /wp-content/plugins/buddypress/bp-themes/bp-default/activity/activity-loop.php (around line 38) This assumes you're using the default theme, if not, do it in your other theme file.
// Change:
<li class="load-more">
<a href="#more"></a>
</li>
// For this:
jq('.pixelMonitor').remove();
jq(document).unbind('scroll');
// 2) Add this at the bottom of that file:
<div class="pixelMonitor" style="width: 1px;height: 1px">
<div id="loadingActivityMessage" style="background-color: white;float: right;height: 16px;padding: 4px 2px 4px 39px;width: 100px">Loading...</div>
</div>
/* Auto load more updates at the end of the page when reaching the bottom of the page */
jq(document).ready( function() {
iterationAllowed = true;
function loadActivityOnScroll(){
jq("#loadingActivityMessage").show();
if ( null == jq.cookie('bp-activity-oldestpage') )
jq.cookie('bp-activity-oldestpage', 1, {path: '/'} );
var oldest_page = ( jq.cookie('bp-activity-oldestpage') * 1 ) + 1;
jq.post( ajaxurl, {
action: 'activity_get_older_updates',
'cookie': encodeURIComponent(document.cookie),
'page': oldest_page
},
function(response){
jq("#loadingActivityMessage").hide();
jq.cookie( 'bp-activity-oldestpage', oldest_page, {path: '/'} );
jq("#content ul.activity-list").append(response.contents);
}, 'json' );
return false;
};
jq(document).scroll(function(){
if ( Math.round(jq('.pixelMonitor').last().offset().top) > ( jq(document).height() -500 ) && iterationAllowed === true ) {
loadActivityOnScroll();
iterationAllowed = false;
setTimeout('iterationAllowed = true', 3000);
};
});
}); /* Auto load more activity block ending here */
Hope you enjoy it. In near future I hope I’ll have it as a plugin and I’ll post it here to let you know.
Some demo: http://www.horizontea.com/ (scroll to the bottom to see in action).
PS: I’m not saying this is bug free, but will not affect any data on your db or installation, it just tweaks the interface 
Cheers!
PS 2: As soon as I check the “WP/BP” way to add this code to the file “automatically” (as a plugin) I’ll update it.
