There are whole bunch of stuff one can use if one is willing to DIY. I wasn't.
One of the easiest thing I thought of was to use a small air pump and hook up this air bulb thing. Just the tip end. Unlike solenoid or servo, you get to dampen the shock by actuating with air. There is a small air pump in all those automated blood pressure gauges suitable for this use. I wanted to avoid "kuchunk" type thing as it has a chance of transmitting this sudden shock to the camera body.
If you want to go the car parts route, Mercedes-benz vehicle from the 90s used pneumatic pump system for doors and trunks. (also fuel cap flap). A pump is hidden under the seat.
If the bulb is capable of tripping your shutter with 20' of thin rubber tubing, you may find that you can go to 30' that by replacing the rubber tube with 1/8" vinyl tube. It won't be as soft and easy to roll up, but it'll be a lot more positive.
1/8" I.D by 1/4" O.D, A bit stiff and bulky, but commonly available at local hardware stores:
Slightly more flexible (3/16" O.D.)
For super flexible, absolutely guaranteed not to "balloon" like rubber tube, use Polyurethane tubing.
The 1/16" I.D. will assuredly give you double the useable length of your bulb. It might be a bit sluggish to fill the cylinder, but it WILL guarantee full pressure to trip the shutter. And it will probably coil up just as small as the rubber tubing...
A friend sounds the the easiest solution by far!
You are forgetting the fact that this is APUG, an enthusiast forum... We need a complicated solution for every problem....
What's so hard about a string and weight to fall on the cable release?
What about a mouse trap?
I have another idea that would not be very expensive and with a little tinkering could work and that is to use a mouse trap. The tension on the spring would not have to be as much as is needed to kill a mouse, so perhaps the spring could be cut down or replaced with a less powerful one. Then a string is tied to the tripping device and could then be any length. This is similar to the weight being released as one person suggested, but the advantage is that no weighty object is needed. The wood base of the mouse trap would only need a small hole drilled through it where the bar comes down that kills the mouse, and that could be padded a little so as to not be like a hammer coming down on a nail. Another way of doing this would be to use a spring loaded clothes pin with a piece of wood or metal in the jaws of the pin. A metal piece would be glued to the top of the clothes pin which would come down on a cable release where all this is mounted on a board. The only problem with any of these is the string would have to be kept out of the picture. That might required a pulley system. I'll try to come up with something else too. Ric.
OK... more complicated Ruth Goldberg device....
A trick will be.... how do I stop myself and my partner (who will be in the photograph) from making amazed look as the device functions and burst out laughing when it successfully works. That'll make an amazing photograph....
Seriously though, the bulb system seems to work amazingly well. Plenty of reserve air. I'm going to try that first.
The only thing I had to do with an air release was adjust the return spring.
I was trying to use it with a Pentax A3 for drive-by photography (as you can get some very different perspectives from a camera poking out of your car window) but on test it kept holding the shutter button down for two or three shots rather than releasing it as soon as I stopped squeezing the bulb. The A3 is an oddball in that it has an auto winder built-in and uses a standard cable release, the other Pentax bodies use dedicated remote releases (hence why I used it).
I stretched the return spring and it worked perfectly for one roll before the camera split a drive gear. Oh well, at least the air release fits all my other manual focus bodies!