Broadband Phone (Internet phone adapter)

[#1]

Hi,
I'd like to use my normal house phone's to make my Voip calls without my PC being on all the time - when l was shopping at the wknd Tesco's had this product on offer:
(Internet phone adapter - IPA1000)
http://www.tesco.com/internetphone/products_internet_phone_adapter.html#top
I was just wondering if it was only compatible with Tesco's packages and if anyone is already using something like this plugged into the router to make voip calls?
Any advise on what to buy / use would be greatfull

[#2]

I personally have a linksys pap2 bought from broadband buyer http://www.broadbandbuyer.co.uk/Shop/Search/SearchResults.asp?SearchColumn=&QSearch=linksys%20pap2
It has worked seamlessly with plusnet voip and was simplicity itself to setup.
When I was originally looking for a voip solution I came across a lot of these or similar switches that had hacked firmware, try ebay as a lot of these were supplied by voip phone providers at free but were locked to that supplier then firmware hacked to open them to any isp.
You could prob get one for about £10, as for the tesco one I'm guessing here but at that price its probably locked to tesco.
I have a bt voyager thats been unlocked, so if you can get hold of one of them, theres a few about as these were bundled with BT broadband.
Let me know if u you can and I'll send the hacked firmware.
BTW not illegal.