Electronically fuel-injected gasoline engines solve this by using two ECUs. If one misbehaves the pilot can switch to the other. An ECU check is part of the runup checklist, just like a magneto check. You could probably achieve the same thing with a diesel; it's just a matter of money and engineering time.

Also, there are planes flying around without redundant ignitions. I think it depends on what kind of certification the aircraft needs.

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1981 Mercedes 300TD, 1994 Honda Civic Del Sol
http://mefi.us/images/fuelly/smallsig-us/67195.pnghttp://mefi.us/images/fuelly/smallsig-us/103885.png

For the most part, gasoline aircraft engines do not have redundant fuel systems. No backup carburetors or fuel injection systems. The only system that is completely redundant (usually, but not always) is the ignition system, which is not applicable to a diesel engine.

I'll keep that in mind next time the FAA asks me for mine!

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'70 F100 shortbed
'82 Diesel Westy
'83 Euro 300TD
Curtlo Viper
Yeti ARC
Surly long haul trucker

You do have 2 fuel pumps in some aircraft. One mechanical and one electrical. That would be the only example of a redundant fuel system.
Dual magnetos do more than provide redundant ignition systems. The plugs are spaced as to provide complete combustion of the fuel charge. If you run the engine on just one mag the engine will detonate as the flame front speed is not sufficient to complete the fuel burning process before the cylinder has created enough pressure to detonate the rest of the fuel.
Bad for the engine but much better for the pilot than having no spark at all!

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'70 F100 shortbed
'82 Diesel Westy
'83 Euro 300TD
Curtlo Viper
Yeti ARC
Surly long haul trucker