HK has a multi tool for their 416. According to one post on HKpro.com, it costs $863! That is a bit high for what looks like just a castle nut wrench, spanner wrench and muzle device wrench all in one. It does not even have the torque wrench or a socket wrench with it. You must provide you own. I know some H&K accessories are rather pricey but this seems a bit much for hunk of metal.
You could get the Gerber AR Short Stack and accomplish most if not more with the Gerber than this HK416 tool. Although, the Gerber AR Short Stack is lacking a spanner wrench for the barrel nut.
Nathan S. wrote an article about the Gerber Short Stack.