Why would it be any more dangerous than a regular lawn mower?
Seems to me like it would be great for flat, open yards! I live in an apartment now but support the use of push reel mowers. Noise reduction? Check. Battery/combusion engine replacement? Check. Exercise? Check. The "redneck exercise bike" might not be for everyone but I thought it was being lampooned unfairly by the majority (some did think it could be useful).
version 2.0: make the mower a trailer, then you can unhook it when the mowing's done, and ride the bike.
Though I've got an even better idea for version 2.0: make the mower a trailer, then you can unhook it when the mowing's done, and ride the bike.