Yes it's an eheim external with the heating element at the bottom of the canister. You are thinking of the inline heaters that you can attach into a section of piping somewhere e.g. the hydor one? Extra connections for poss leakage, and does it reduce flow rate (don't know), would put me off that rather than the rena smartheater which replaces the intake, but don't know anyone who uses one.
Mmmm, I've heard some negative things about the Hydor external heaters failing. I'd love to have the heating outside the tank, because heaters aren't very nice to look at, but replacing 4 externals for the heated version and buying more for the other tanks is a stretch too far financially. I might have to do it on a maintenance basis - when a filter needs replacing/upgrading may be do it then, piecemeal. But with Eheims being so reliable that may take years
Good price that, but do they have a thermal cutout? I've started buying these and now they don't go 'bang' if they run dry, but the glass will still shatter if you take them from warm (25C) water to cold water (5C) as I found out... (doh!) I also got a digital heater from a LFS that was closing and got 50% off. I wouldn't have paid ?40 for it but ?20 was a bargain, it's my pride of place heater! :)