Hi jonradio,
Apologies for the delayed response. Busy weekend with slow start this week. :-)
Thank you for doing further research on the alternatives. While the mobile detection plugins you pointed out are great, they're not what we're looking for. We already have a device detection algorithm (old though) that will send visitors to separate mobile/WAP sites depending on their device type (feature phone, android, iphone, etc.). It is working well for our situation now, though we are looking to upgrade the whole setup using a newer device detection algorithm like the ones you pointed out. The one from 51degrees looks especially mighty! Thanks for pointing that out!
The mobile themes plugins are also something we are looking at, though that's for the future and our WP site is already responsive using http://themeawesome.com/responsive-wordpress-theme/ with a custom child theme.
The reason we were using your plugin is because, we needed to keep the current redirection settings to the WAP sites, while being able to serve the WP site/pages from those WAP sites via an iframe. The more specific requirement is that we are using a glossary tooltip plugin that has a mouse-hover pop-up of special terms that won't work outside of the WP site. We've explored using APIs, but that doesn't seem to be a solution as well.
That said, we're also looking into creating a PHP script (in the mobile/WAP site) to auto-append the trailing ?keyword=value on subsequent clicks within the iframe. Not sure how feasible that is, but it looks like being able to do that from the WP side is the best solution, thus the question in this thread in the first place. Please let me know your further thoughts on this.
On a related note, have you ever measured if there are any performance hits when using this plugin?... in other words, any difference in page load time using default theme vs alternate theme via ?keyword=value ? (obviously not easy to measure as each theme has their own weight), but perhaps, you know the stats from the way the plugin is coded and the alternate theme is summoned upon.
Thanks again!
~Bowo