Am getting a gps for speed measurement to determine optimal paddle length and to improve stroke technique, not for navigation.
Can’t think of any…
...of the several different pocket GPS models I've used that won't do what you are describing.
You should be able to find speed measurement settings in the setup screen. All models I've seen have an option on the trip screen (or whatever it's called on the particular unit) to show several small fields or one large one. Presumably, you would choose KPH in the units of measure or speed list, and choose speed for the one field you get in large font when you choose the single field option on the trip data screen.
That's about a generic as I can think to answer those questions. You should probably just pick a pocket unit you like for other reasons and have someone show you whether it will do what you want (it probably does). I recommend Garmin units - 76 series or 60 series. Very durable and easy to use.
Oh - and all the pocket units I've seen have an option to turn off sounds.
When I am training,
I use a Garmin Map 76 and set it to two windows.
One for Speed, and the other for distsnce.
The numerals are about a inch high, and that is good for these old eyes.
Your second question doesn’t make sense to me.
there is no “filter” setting on a GPS for what you are talking about.
I can download my tracks, and they will give me a given speed for just about every second of my trip, but that is about it.
Cheers,
JackL
filter and noise
I think he’s asking about adjusting the averaging time for the speed. Instantaneous GPS speed readings will sometimes jump around a bit because of the random variability from one position to the next (the noise he’s referring to). I believe GPS units eliminate this by calculating speed by not just comparing where you are this second to where you were last second to get speed. Instead, they compare your average position over the last couple seconds to your average position over the next couple seconds. The result is a much more accurate speed reading that doesn’t erratically jump from 10 knots to 1 knot.
I have seen some bigger fixed-mount GPS units that allow you to adjust how much averaging they do, but I haven’t tried to do it on handhelds, so they may offer the same option, or maybe not. Don’t know. Of the various Garmin GPS units I’ve used, I’ve always found the default settings for speed to be sufficiently dampened, but also sensitive enough to tell in a second or two if tweaking that sail, or increasing your cadence had an effect on speed.
same screen
I ilke the garmin 76 with speed and distance programmed on same screen. With 4in strip of aluminum held on with gorilla tape, I made a bracket with a hole that bolts to front rim of boat. Or use electrical conduit clamp to fasten on bar of canoe. Speed and distance on same screen is a must. So are buttons out front so you can use them with gloves.
Speed Filter
The Garman 76 manual is at http://www8.garmin.com/manuals/GPS76_OwnersManual.pdf
There is a section on the Speed Filter which can be set to Auto or User. In User there is a seconds field where the averaging time can be set. I presume there is a best setting for speeds in the kayak range. Has anyone with this gps played with the averaging time?
bracket
There is a suction bracket that is about $25 that I was thinking of getting.
Also, no gloves required in San Diego.
Delorme PN-40
I’ve grown to really love the Delorme PN series of handheld gps. Nice large screen with alot of options. Many that I dont use. When I paddle I mainly leave mine on a screen that shows:
Current Speed
Average speed
Total trip time
trip moving time (doesn’t count stops)
distance
Not sure about the filtering your talking about.
The series also comes with some amazing software and is very waterproof.
I fully submerged mine for 10min in the sink the day I bought it. Just to test it. They say its waterproof for up to 30min I think but I figured if I dont find it within 10min I’m not going to. 
Nice GPS for the money definetly worth a look.