@tw_sjo I have a surplus OVMS unit (plus GSM antenna, GPS tracker antenna, and Pickit 2 programming tool) after moving to Kenneth's Powerbox ("PB"). Although it needs an amount of programming (it doesn't work straight out the box like the PB), one can achieve similar benefits on the OVMS at a fraction of the price.
People have been known to deride the OVMS for its need of a SIM card to programme/change settings. This does not necessarily mean that the OVMS needs a dedicated SIM; one can insert a "donor" phone SIM temporarily (whilst using another phone to send the programming SMS messages) to programme and simply returning the SIM to the "donor" phone once complete.
After programming the Twizy's Sevcon, the OVMS unit (like the PB) can be unplugged. These alleviates a drain on the 12v battery.
I still very much rate the OVMS unit. Fortunately I had sufficient spare cash to buy the more use-friendly PB.
If anyone is interested in buying my OVMS, either PM me or leave a post here.