Sig Sauer has very recently come out with the 556xi modular setup of pistol/rifles, specifically with their 10inch SWAT 556xi pistol that comes with a SIG Brace from the factory. Sig also offers a good bit of variation in this setup and others. This setup has an ambi-charging bolt setup and if you are creative enough you can find a way to fold that tube since it is not being used. Sig also has other variations of their pistol setup, they have a M400 SWAT pistol in 11inch and 7.5inch setup. They also have a .300blk pistol and a 762x51 12inch setup. This 556xi line has the same setups, except with added 762x39 Russian line. Sig dove head first into this whole thing and started the craze once the ATF allowed the SIG Brace to stay on the market.
As I posted below, Daniel Defense just released a pistol version of their MK18 rifle.
I like the MK18 setup, coming at a barrel length of 10.3inches, does not come with a SIG Brace, however and priced at around $1700 from the factory. Looks like it'll be a nose-to-charging handle type of setup with the brace.
BCM has also released a Pistol Buffer Tube specifically targeting the SIG Brace crowd.
Aero Precision COP C4 Upper
Aero Precision make this one piece upper that will take a 7.5inch barrel plus muzzle device specific for the AR pistol crowd. You can buy that and one of their lowers (like the pewpewpew lower I bought) and you have yourself a fine pistol setup!
When you are talking about AR15 pistols, specifically, to point out that there are top tier AR15 manufacturers making them.
Primary Weapons Systems MK1 Pistols
These come in 7.5inch, with a SIG Brace already attached, it also comes in 10.75inch which puts the whole pistol in 26inches OVA. You can also get a .300BLK in 9.75inch. You might be wondering why it is so expensive? Long stroke piston system. Light years ahead of anything anyone else is doing and in a 7.5 setup is gold.
Primary Weapons Systems DI Pistol
Yes, they make a DI AR platform as well, only at 10.75inch however, again comes with a SIG Brace from the factory.
I will update this post when I find more companies that are making OEM AR15 pistol items/complete rifles.