I was trying to get a computer to work on my wife's V-Rex when I realized the distance from fork to handlebar is probably too long. The computer's specs say the wireless range is only 70 cm. Is there a model of wireless cycle computer that works with a recumbent?

Yes, it's called a Garmin GPS. All the others are typically either too short a transmit range, or are badly affected by LED lighting. Look for a Garmin Edge 305 as a starter GPS, that can be had for well under $100 on ebay used. Plus she can use a HRM with it if she wants that data too, and it is cadence compatible.

Contact https://hostelshoppe.com/ Talk to them on the phone and have your measurments ready XD

Try asking the question in the technical discussion section of www.bentrideronline.com . There has to be somebody there who has already solved the problem for you.

I just received a nice $7.39 wireless computer to use on my Catrike 700 trike. The information posted for the same computer sold on Ebay says 60 cm maximum separation. I have used wired computers on a different trike by adding a two foot section of wire so that the sensor could be by the rear wheel and the readout on the USS handlebar. That one worked fine for several years. The wired version of the one I purchased is available for $4.85 (SKU026780) if you wanted to experiment on it by lengthening the wire. The downside is that the China supplier (www.banggood.com) takes about 30 days for the order to reach the US. Shipping is free on all products and I did not get charged any duty or currency conversion charge. It says "China post air mail" but they must use carrier pigeons for air mail!

I have 3 wireless digital signal VDO computers on three 'bents. Digital computers have longer effective signal ranges than analog.
(C2DS and C3DS) Not sure how available those are. More current model: https://www.amazon.com/VDO-X3DW-Wirel.../dp/B0021QIYB8

I just went with a wired computer. Simple and cheap.

Battery costs much much much lower over time for wired units.

For wired units. get the longer wire made for tandems. I have a Cateye digital and it works fine. I think the distance is good to 10 meters.