I do not think there is any one perfect solution to this problem, but I do believe crew resourse managment, which also applies when you are by yourself, is one of the better ideas.  There are numerous instances of multi thousand hour flight crews landing gear up with the gear warning horn screaming in the background.  I recalled just a couple years ago a 747 on final to JFK and the controller spotted the gear not down, and you can hear the horn going off in the ATC transmitions and it took the controller to spot the gear and multiple radio calls to convice the crew the gear was not down and to go around.  Just like someone said about the legacy not slowing down, I used to teach in the 747-400 and I don't know how you could get that plane on final without the gear down other than completely ignoring all standard operating procedures and checklists, but it does happen.  Since I fly alot of different aircraft, from my early days I have beat into my head a GUMPS check on base, final and short final.  Even in fixed gear aircraft I call out this procedure verbally either with someone or by myself, and I still find myself checking the gear position as I am starting my flare.  I believe that only doing it once, a simple distraction is all it takes to miss it, but doing it 3 to 4 times, throughout the approach profile, either IFR or VFR, you should catch it at some point.  When shooting approaches, I always do gear and flaps at the FAF, then I do a 1000ft call, checking for a stabilized approach and landing checklist again, then at minimums a last GUMPS check.  Nothing is perfect, but maybe this could help.  I have not had my gearup "yet", but I keep beating procedures into my head and recognize when I am distracted, reset my brain and start again.  Most airline CRM procedures are much easier in a two crew cockpit with someone else to run the checklists and the pilot flying to respond, but there are alot of good points that can be adapted to single pilots operations.

Fly safe
Luke Alcorn