RTI has announced one, but it is RF and needs a base station inside, so I am not sure it is going to be any cheaper than than the Balboa Dolphin. You can see it here:

[Link: rticorp.com]

Infrared Remote Solutions claims to have something on the way, though that has been up on their Web site for quite some time now with no further details forthcoming:

[Link: infraredremote.com]

All in all, I suspect the Dolphin is the only game in town right now.