Lightweight Bitcoind?

[Valzador]

Say I want to start run a server which requires a bitcoin wallet to check balances, send and receive coins.

What other alternatives are there instead of downloading 70GBs of bitcoin data.

[2c0de]

You can activate pruning. This way you can prune your chain to as small as few GB.

Only disadvantage, you have to refresh your wallets from time to time, to prevent wallets becoming outdated (when recovering blockchain from backup).

[NeuroticFish]

Say I want to start run a server which requires a bitcoin wallet to check balances, send and receive coins.

What other alternatives are there instead of downloading 70GBs of bitcoin data.

One thing that comes into my mind is to us Blockchain wallet and its API for it.
There is even example source code for it.
And if you are not comfortable to use their wallet (I wouldn't be), just watch that wallet and when a threshold amount is reached, transfer it to your main / safe wallet.

[BigBoom3599]

I think your best options are to either use the pruning mode with a full bitcoin node, or use an SPV wallet that offers an API.

[hexafraction]

...or use an SPV wallet that offers an API.

If your server application is written in Java (or you're OK with making some sort of interface between whatever you're using and a Java-based daemon) then bitcoinj may be appropriate for this case. It's an SPV client but additionally allows programmatical access to more than you may get with a simple SPV client (such as block, txn, address info, and so on). You'll still end up downloading tons of block headers, but that's unavoidable without completely delegating chain operations to someone else.