Seb... this plan allows you to recharge the phone from the cell OR a landline OR online (as well as you can buy prepaid cards to punch in) from anywhere. ;-) I've used it for over a year and never had a bit of trouble. It pops your time-minutes up each time you turn it on etc so you aren't caught short etc.
Takes about 2 mins to recharge via the phone and about 1 minute if you do it online.
We weighed the time it would need to be used versus a contract and a set amount per month and this one won hands down. At least read in to the site and compare it to the contract costs etc. If you don't use it that often, then its the better deal by far.
You might be thinking of those rinky throwaways I have seen.