I would recommend the Boss FS-6 for a dual footswitch.
The choice of expression pedal depends on what kind of sweep range you find most comfortable/effective. I like the Yamaha FC7 for its unusually wide sweep because I feel like it gives me more precise control, but some might find it uncomfortable and prefer a more Crybaby-like sweep range. The FC7 is also pretty rugged and has some heft to it, so if you're trying to keep your gigbag light that might be a consideration.
I've had great results using a Moog EP-3 expression pedal. Only $40.
I've had no problems with the Moog EP-3 as well. For the bucks it's a great buy. I have recently switched over to the Mission Engineering EP-1 for Kemper simply because it includes a toe switch, which is great for quickly setting to "boost" or whatever your global needs might be. It's also built like a tank but pricier ($129). It also requires use of one TRS cable plus one regular guitar cable.
The new Dunlop Volume/Expression pedal is excellent.
Andy, if you don't need ultrafast switching try a double-switch pedal from any amp: you'll need to press it twice every time, but it works for me: it's like double-clicking the mouse buttons 
If you have any soldering experience - make one.
Here is a good example -
[quote='burningyen','http://www.kemper-amps.com/forum/index.php/Thread/16569-Switches-and-Expression-Pedals/?postID=172170&#post172170']I would recommend the Boss FS-6 for a dual footswitch.
The FS-6 is a goog recommendation, I use two of them (for X-Slot, Mod-Slot, Delay, Rev) The only disadvantage for the FS-6 is, it has no power supply, just only an internal 9-Volt-battery.
I installed a Micro-Jack for 9-V-Power Supply for both pedals (rather easy) and use them together with the FCB1010.
(much cabeling for this constellation, I can tell)
I'm waiting for the upcoming KFC
A WORD OF WARNING!!
While I love the toe button functionality of the Mission Engineering EP1-KP, I made an email suggestion to the company that they put a little LED on it so you're sure when it's on. Simple and useful, right? Well they wrote back that they indeed already made one, the SP-1. OK, I'm thinking, great. So I ordered that up directly from them - only the switch, which does light up, will NOT WORK WITH THE KPA!! Don't buy it! Not only did it not engage the switch feature - a fact left out by whoever at the company pointed me towards this other pedal - the CEO himself refused to pay for my shipping charges, to return it. I am not thrilled with this, to put it mildly!
Yes it was my mistake for ordering direct and I should have called them up and investigated more, perhaps believe what they claimed less ... it won't happen again! I am personally boycotting Mission Engineering from now on. Horrible policy - they obviously care more about a few bucks than having happy, repeat customers. I hope others in the community will heed this warning and not get burned by them.
Yeah... this is something that always leaves me speechless. And it's a plague, specially in Italy and other "third world" places. Greed and stupidity... a killer combination 
Yeah! 
Another recommendation for the FC-7 pedal. No bells and whistles, but you got to love the additional control a little extra throw gives you. As mentioned by burningyen, it's built like a tank. The only silly thing is that the cable is so short, you'll need a TRS female to TRS male extension cable if you want it further from your Kemper.
Yeah I saw that, bummer there.
Ok, this is a BIG minus for Mission Engineering! What a pity.
Actually it's quite ridiculous to charge you for the shipping, Gary.
You're not kidding. They just lost any future purchases from me, that's for sure.
From their user guide:
"The standard SP-1 is fitted with a TRS latching foot switch."
Switch
Type - Latching
Function - Toggles tip between ring and sleeve
The Kemper wants to see two Momenatry switches that makes contact like this:
1) Ring to Ground.
2) Sleeve to Ground.
Even if it had a single momentary switch, though, it still would not be completely compatible with the "dual momentary" switch idea of the TRS jack on the back of the Kemper, because it is just one switch.
I realize that now, Paul, my mistake. I believed their comments that they "had my solution" already... my stupid for not investigating their claims,
HEY -
Try this. (from the EP1-KP manual) The EP1-KP *is* their solution for Kemper users.
Use of the internal footswitch is optional. To use the
footswitch, connect OUT2 to switch/pedal input 2
on the rear panel of the amplifier using a standard
mono (TS) ¼” guitar or patch cable.
If they sent you a pedal with a momentary switch in it, it may very well work.
Oh don't worry, that's exactly how I've been using the EP1-KP - with toe switch for effect X -post amp pure booster. It works just fine, just was trying to find a little LED along with it like any normal stomp... my bad!! LOL
But thanks for the help. Hope all is well is Paults-land!
Gary - I just read that other thread. My condolences!
Play on, my friend 
